岡山大学農学部 Acta Medica Okayama 2186-7755 112 2023 Streptomyces属放線菌由来の高基質特異性l-グルタミン酸オキシダーゼに関する研究 13 18 EN Natsume Nakayama Course of Agrochemical Bioscience K. Inagaki l-glutamate oxidase (LGOX) from Streptomyces sp. is a heterohexameric flavin enzyme that catalyzes the oxidative deamination of l-glutamate to form α-ketoglutarate with ammonia and hydrogen peroxide. LGOX shows strict substrate specificity for l-Glu. In addition, it is highly thermostable and pH stable. Because of these properties, LGOX is currently used as a biosensor for the trace determination of l-Glu in the food industry and clinical laboratories. The full-length cDNA is 2103 bp and is encoded by a single polypeptide chain consisting of 701 residues including subunits α-γ-β. The LGOX gene was heterologously expressed in Escherichia coli JM109. The LGOX precursor expressed in E. coli is a homodimer with weak enzymatic activity and becomes a heterohexamer upon activation by protease treatment. X-ray crystallography and docking studies of purified recombinant LGOX suggest that the Arg305 residue is a key residue for substrate recognition. Mutant analysis showed that Arg305 is essential for substrate recognition, as the activity toward l-Glu was greatly reduced and substrate specificity was changed in some enzymes. The functional analysis of R305E-LGOX, which is an l-Arg oxidase, revealed that R305E-LGOX can be used as a enzyme biosensor for l-Arg. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 2186-7755 111 2022 糸状菌Trichoderma viride由来の抗腫瘍性酵素L-リシン α-オキシダーゼに関する研究 7 14 EN Masaya Saito Course of Agrochemical Bioscience Kenji Inagaki L-Lysine α-oxidase (LysOX) from Trichoderma viride is a homodimeric flavoenzyme that catalyzes the oxidative deamination of L-Lysine to produce α-keto-ε-aminocaproate with ammonia and hydrogen per-oxide. LysOX inhibited the growth of cancer cells but showed relatively low toxicity for normal cells. The full-length cDNA consists of 2,119 bp, and encodes a long N-terminal propeptide composed of 77 resi-dues (Met1-Arg77) and the mature protein (Ala78-Ile617). The LysOX gene was heterologously expressed in Streptomyces lividans TK24 or Escherichia coli SoluBL21. The enzymatic properties of the purified recombinant LysOX, such as substrate specificity, kinetic parameters and thermal stability, are the same as those of the native LysOX. The LysOX precursor (prLysOX) expressed in E. coli shows weak enzymatic activity and is activated by proteolytic processing. The crystal structure of prLysOX revealed that the propeptide of prLysOX indirectly changes the active site structure to inhibit enzyme activity. Moreover, the crystal structures of LysOX and its L-Lysine complex revealed that the hydrogen bonding network formed by Asp212, Asp315 and Ala440 with two water molecules is responsible for the recogni-tion of the ε-amino group of L-Lysine. In addition, a narrow substrate-binding site and acidic surface at the active site entrance both contribute to strict substrate specificity. Mutational analysis demonstrated that Asp212 and Asp315 are essential for substrate recognition, and the D212A/D315A LysOX prefers aromatic amino acids. Furthermore, the structural basis of the substrate specificity change has also been revealed by the structural analysis of the D212A/D315A LysOX and its substrate complexes. No potential conflict of interest relevant to this article was reported.

Elsevier Acta Medica Okayama 25901524 5 2021 Structural basis of enzyme activity regulation by the propeptide of l-lysine α-oxidase precursor from Trichoderma viride 100044 EN Masaki Kitagawa Department of Macromolecular Science, Graduate School of Science, Osaka University Nanako Ito Department of Macromolecular Science, Graduate School of Science, Osaka University Yuya Matsumoto Department of Biofunctional Chemistry, Graduate School of Environmental and Life Science, Okayama University Masaya Saito Department of Biofunctional Chemistry, Graduate School of Environmental and Life Science, Okayama University Takashi Tamura Department of Biofunctional Chemistry, Graduate School of Environmental and Life Science, Okayama University Hitoshi Kusakabe Enzyme Sensor Co., Ltd. Kenji Inagaki Department of Biofunctional Chemistry, Graduate School of Environmental and Life Science, Okayama University Katsumi Imada Department of Macromolecular Science, Graduate School of Science, Osaka University Harmuful proteins are usually synthesized as inactive precursors and are activated by proteolytic processing. l-Amino acid oxidase (LAAO) is a flavoenzyme that catalyzes the oxidative deamination of l-amino acid to produce a 2-oxo acid with ammonia and highly toxic hydrogen peroxide and, therefore, is expressed as a precursor. The LAAO precursor shows significant variation in size and the cleavage pattern for activation. However, the molecular mechanism of how the propeptide suppresses the enzyme activity remains unclear except for deaminating/decarboxylating Pseudomonasl-phenylalanine oxidase (PAO), which has a short N-terminal propeptide composed of 14 residues. Here we show the inactivation mechanism of the l-lysine oxidase (LysOX) precursor (prLysOX), which has a long N-terminal propeptide composed of 77 residues, based on the crystal structure at 1.97 Å resolution. The propeptide of prLysOX indirectly changes the active site structure to inhibit the enzyme activity. prLysOX retains weak enzymatic activity with strict specificity for l-lysine and shows raised activity in acidic conditions. The structures of prLysOX crystals that soaked in a solution with various concentrations of l-lysine have revealed that prLysOX can adopt two conformations; one is the inhibitory form, and the other is very similar to mature LysOX. The propeptide region of the latter form is disordered, and l-lysine is bound to the latter form. These results indicate that prLysOX uses a different strategy from PAO to suppress the enzyme activity and suggest that prLysOX can be activated quickly in response to the environmental change without proteolytic processing. No potential conflict of interest relevant to this article was reported.

Springer Acta Medica Okayama 1436-2228 2020 Comparative Gene Analysis Focused on Silica Cell Wall Formation: Identification of Diatom-Specific SET Domain Protein Methyltransferases EN Michiko Nemoto Graduate School of Environmental and Life Science, Okayama University Sayako Iwaki Graduate School of Environmental and Life Science, Okayama University Hisao Moriya Graduate School of Environmental and Life Science, Okayama University Yuki Monden Graduate School of Environmental and Life Science, Okayama University Takashi Tamura Graduate School of Environmental and Life Science, Okayama University Kenji Inagaki Graduate School of Environmental and Life Science, Okayama University Shigeki Mayama Department of Biology, Tokyo Gakugei University Kiori Obuse Graduate School of Environmental and Life Science, Okayama University Silica cell walls of diatoms have attracted attention as a source of nanostructured functional materials and have immense potential for a variety of applications. Previous studies of silica cell wall formation have identified numerous involved proteins, but most of these proteins are species-specific and are not conserved among diatoms. However, because the basic process of diatom cell wall formation is common to all diatom species, ubiquitous proteins and molecules will reveal the mechanisms of cell wall formation. In this study, we assembled de novo transcriptomes of three diatom species, Nitzschia palea, Achnanthes kuwaitensis, and Pseudoleyanella lunata, and compared protein-coding genes of five genome-sequenced diatom species. These analyses revealed a number of diatom-specific genes that encode putative endoplasmic reticulum-targeting proteins. Significant numbers of these proteins showed homology to silicanin-1, which is a conserved diatom protein that reportedly contributes to cell wall formation. These proteins also included a previously unrecognized SET domain protein methyltransferase family that may regulate functions of cell wall formation-related proteins and long-chain polyamines. Proteomic analysis of cell wall-associated proteins in N. palea identified a protein that is also encoded by one of the diatom-specific genes. Expression analysis showed that candidate genes were upregulated in response to silicon, suggesting that these genes play roles in silica cell wall formation. These candidate genes can facilitate further investigations of silica cell wall formation in diatoms. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 2186-7755 109 2020 Marinomonas mediterranea由来キノン含有新規グリシンオキシダーゼの大腸菌発現系の確立と性質検討 1 6 EN Yuki Kajiyama Graduate School of Environmental and Life Science, Okayama University Satsuki Mizobata Graduate School of Environmental and Life Science, Okayama University Shusaku Akaji Graduate School of Environmental and Life Science, Okayama University Michiko Nemoto Graduate School of Environmental and Life Science, Okayama University Takashi Tamura Graduate School of Environmental and Life Science, Okayama University Kenji Inagaki Graduate School of Environmental and Life Science, Okayama University 　Novel glycine oxidase (GlyOX) from Marinomonas mediterranea depends on cysteine tryptophilquinone (CTQ) and catalyzes the oxidative deamination of glycine to produce a glyoxylate, ammonia, and hydrogen peroxide. M. mediterranea GlyOX genes (goxA and goxB) were cloned and recombinant GlyOX was heterologously expressed by E. coli. The purification of recombinant GlyOX was carried out by metal affinity and DEAE-Toyopearl 650M column chromatographies. M. mediterranea GlyOX was homotetramic with a molecular mass of 76kDa and showed optimum activity around 30°C and at pH 5.0, and stability below 50°C and between pH 5.0 to 9.0. M. mediterranea GlyOX shows a strict substrate specificity toward glycine, and the Michaelis constant for glycine was 0.5mM. M. mediterranea GlyOX could determine the quantity of glycine in human serum and human blood plasma with high sensitivity. This study revealed the catalytic and structural properties of M. mediterranea GlyOX with high substrate specificity. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 2186-7755 105 2016 大学生の朝食欠食習慣の統計解析と改善への新指針 1 5 EN T. Tamura T. Ibi K. Inagaki Y. Kubo K. Okuda This study investigated the current status and causes underneath the life of university students who tend to lack breakfast at a relatively high frequency, and statistical analysis on consequences leading to such lack of well-nourished eating habitat in their university life. In October 2014, self-assessed questionnaires were administered to over 150 faculty students. It contained questions about breakfast habits, time allowance for the morning class, and lunchtime setting in their high school timetable. Breakfast states were clearly separated in three groups : 68% of students regularly have breakfast throughout the weekdays, 21% students skipping the breakfast occasionally, and 11% student no habit for breakfast at all. The survey on the high school lives revealed that 70% students used to have lunch 30 min later than the lunchtime set in the university timetable, 7% of them had the lunch time even more than 1 h later. Lunchtime varies among high schools, and statistical significance was revealed (p<0.01) that schools with higher deviation scores tend have late lunch beyond 12: 30. Accordingly, university students were given directions to prepare for the timetable reform on postulation of having lunch time over one o’clock. After continuous survey on the breakfast habits during the second semester, more than 90% of students established the habit of breakfast regularly in their university lives with the improved consciousness toward well-balanced healthy breakfast contents for their higher level of education quality. No potential conflict of interest relevant to this article was reported.

Nature Publishing Group Acta Medica Okayama 2045-2322 6 2016 Molecular evolution of gas cavity in [NiFeSe] hydrogenases resurrected in silico 19742 EN Takashi Tamura Naoki Tsunekawa Michiko Nemoto Kenji Inagaki Toshiyuki Hirano Fumitoshi Sato Oxygen tolerance of selenium-containing [NiFeSe] hydrogenases (Hases) is attributable to the high reducing power of the selenocysteine residue, which sustains the bimetallic Ni–Fe catalytic center in the large subunit. Genes encoding [NiFeSe] Hases are inherited by few sulphate-reducing δ-proteobacteria globally distributed under various anoxic conditions. Ancestral sequences of [NiFeSe] Hases were elucidated and their three-dimensional structures were recreated in silico using homology modelling and molecular dynamic simulation, which suggested that deep gas channels gradually developed in [NiFeSe] Hases under absolute anaerobic conditions, whereas the enzyme remained as a sealed edifice under environmental conditions of a higher oxygen exposure risk. The development of a gas cavity appears to be driven by non-synonymous mutations, which cause subtle conformational changes locally and distantly, even including highly conserved sequence regions. No potential conflict of interest relevant to this article was reported.

the American Society for Microbiology Acta Medica Okayama 2169-8287 3 4 2015 Draft Genome Sequence of Streptomyces incarnatus NRRL8089, which Produces the Nucleoside Antibiotic Sinefungin e00715-15 e00715-15 EN Kenshiro Oshima Masahira Hattori Hitomi Shimizu Koji Fukuda Michiko Nemoto Kenji Inagaki Takashi Tamura A draft genome sequence of Streptomyces incarnatus NRRL8089, which produces the nucleoside antibiotic sinefungin, is described here. The genome contains 8,897,465 bp in 76 contigs and 8,266 predicted genes. Interestingly, the genome encodes an open reading frame for selenocysteine-containing formate dehydrogenase-O and the selenoprotein biosynthetic gene cluster selABCD. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 2186-7755 103 2014 高基質特異性L-グルタミン酸オキシダーゼより作成した基質特異性改変酵素L-アルギニンオキシダーゼの性質検討 5 9 EN Ryuichiro Nakai Shihoko Fujino Tomohiro Utsumi Takashi Tamura Hitoshi Kusakabea Kenji Inagaki 　L‒Glutamate oxidase (LGOX) from Streptomyces sp. X‒119‒6 has strict substrate specificity toward L‒glutamate. Recently, we solved the X‒ray crystal structure of LGOX and this revealed that Arg305 in the active site is the key residue involved in substrate recognition. Therefore, we created 19 mutant enzymes of R305X‒LGOX by saturation mutagenesis. One of them R305D‒LGOX, Arg305 substituted with Asp exhibited oxidase activity for L‒Arg. Optimum pH of R305D‒LGOX mutant enzyme was pH 8.5. Interestingly, the activity of R305D‒LGOX toward L‒Arg was inhibited by phosphate. And furthermore, the substrate specificity of R305D‒LGOX was affected by using buffer. The results of inhibition analysis suggest, that phosphate is a competitive inhibitor of R305D‒LGOX when L‒Arg is used as substrate. Kinetic analysis of R305D‒LGOX showed that Km value and kcat value of R305D‒LGOX toward l-Arg were 0.68 mM and 6.7 s-1 respectively. In this study, we showed that R305D‒LGOX mutant enzyme is a novel l-arginine oxidase and useful for l-arginine biosensor. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 2186-7755 101 2012 好熱性細菌Thermus sp.O-3-1由来耐熱性アミダーゼの精製及び性質検討 1 6 EN Fumiaki Kobayashi Hiroki Aomine Wataru Mizunashi Fujio Yu Takashi Tamura Kenji Inagaki The gene encoding a thermostable amidase (EC 3.5.1.4) from thermophilic bacterium Thermus sp.O-3-1, was cloned and expressed in Escherichia coli JM109. The cloned amidase gene (ami) is 930 bp and encodes a protein composed of 310 amino acids. The protein is predicted to have a molecular mass of 33,089 Da. The amidase from Thermus sp.O-3-1 was purified by heat treatment and DEAE Toyopearl 650M column chromatography. The molecular mass of the native enzyme was estimated to be about 70 kDa by gel filtration chromatography, indicating that the enzyme has a homodimeric structure. The purified enzyme was stable up to 80°C and within a pH range from 7.0 to 10.0. The optimum temperature and pH for enzyme activity were 90°C, and 9.0, respectively. The enzyme was strongly inhibited by the metal-chelating compound EDTA. The activity of the EDTA-treated enzyme was reactivated by the addition of Co(2+), Ni(2+) and Mn(2+) ions. Therefore the enzyme was predicted to be metalloenzyme. Finally, as a result of investigation into substrate specificity, the purified enzyme was suggested to be D-amino acid specific amidase, as it showed higher activity toward D-Leu-pNA than L-Leu-pNA. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254　 100 2011 放線菌Streptomyces sp.590由来l-メチオニン脱炭酸酵素の精製および性質検討 3 7 EN Tomomi Maemura Kumiko Uchitomi Chika Kusaka Junko Inagaki Takashi Tamura Kenji Soda Kenji Inagaki L-Methionine decarboxylase [EC 4.1.1.57] catalyzes the decarboxylation of L-methionine and is a pyridoxal 5’-phosohate(PLP)-dependent enzyme. L-Methionine decarboxylase has been purified 630-fold by DEAE-Toyopearl 650M, Phenyl-Toyopearl 650M and Sephacryl S-300 column chromatographies from Streptomyces sp.590. The enzyme has a dimeric structure with identical subunits of Mr 60,000. This enzyme shows optimum activity at pH7.0 and 45°C, and is stable between pH5.7 and pH9.0. L-Methionine decarboxylase has antitumor activity against RERF-LC-AI and HeLa cells. Ten N-terminal amino acid sequence of L-methionine decarboxylase was determined, and the sequence showed no homology with other reported proteins. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 143 4 2008 Selenite Assimilation into Formate Dehydrogenase H Depends on Thioredoxin Reductase in Escherichia coli 467 473 EN Muneaki Takahata Takashi Tamura Katsumasa Abe Hisaaki Mihara Suguru Kurokawa Yoshihiro Yamamoto Ryuhei Nakano Nobuyoshi Esaki Kenji Inagaki <p>Escherichia coli growing under anaerobic conditions produce H-2 and CO2 by the enzymatic cleavage of formate that is produced from pyruvate at the end of glycolysis. Selenium is an integral part of formate dehydrogenase H (FDHH), which catalyses the first step in the formate hydrogen lyase (FHL) system. The genes of FHL system are transcribed only under anaerobic conditions, in the presence of a sigma(54)-dependent transcriptional activator Fh1A that binds formate as an effector molecule. Although the formate addition to the nutrient media has been an established procedure for inducing high FDHH activity, we have identified a low-salt nutrient medium containing &#60;0.1% NaCl enabled constitutive, high expression of FDHH even without formate and D-glucose added to the medium. The novel conditions allowed us to study the effects of disrupting genes like trxB (thioredoxin reductase) or gor (glutathione reductase) on the production of FDHH activity and also reductive assimilation of selenite (SeO32-) into the selenoprotein. Despite the widely accepted hypothesis that selenite is reduced by glutathione reductase-dependent system, it was demonstrated that trxB gene was essential for FDHH production and for labelling the FDHH polypeptide with Se-75-selenite. Our present study reports for the first time the physiological involvement of thioredoxin reductase in the reductive assimilation of selenite in E. coli.</p> No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254　 99 1 2010 好熱好酸性アーキア Sulfolobus tokodaii 由来シスタチオニン γ-シンターゼの精製及び性質検討 7 12 EN Mai Shinozaki Masahiko Yanagitani Shouichirou Kaneda Daizou Kudou Yuuichi Endou Takashi Tamura Seiki Kuramitsu Kenji Inagaki The gene encoding a cystathionine γ-synthase from Sulfolobus tokodaii was cloned and expressed in Escherihia coli Rosetta-gami (DE3). Cystathionine γ-synthase ［EC 2. 5. 1. 48］ from Sulfolobus tokodaii (stCGS) was purified by heat treatment, DEAE- Toyopearl 650M and Sephacryl S-300 column chromatographies from E. coli transformants. stCGS shows optimum activity at pH 7.0, and is stable between pH5.0 and pH9.0. The optimum temperature of stCGS is above 100℃, and the enzyme showed the remaining activity of almost 100% up to 70℃. The K(m) and V(max) with O-phospho-L- homoserine as a substrate are 0.82 mM and 2.42 U/mg. To analyze the role of Phe 97 in the active site of stCGS, we constructed F97Y, R99C, and F97Y-R99C mutant enzymes. Although native stCGS has no activity toward l-methionine, F97Y mutant enzyme gained the elimination activity toward L-methionine. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254　 99 1 2010 シネフンギン生産菌Streptomyces incarnatus NRRL 8089由来アルギニン変換化合物「オルニチンラクタム」の同定 1 5 EN Koji Fukuda Takashi Tamura Kenji Inagaki Sinefungin is a nucleoside antibiotic, in which a molecule of L-ornithine is linked to the 5' end of adenosine through a C-C bond. The antibiotic was isolated from the culture broth of Streptomyces incarnatus. For the purpose of detecting intermediate of sinefungin biosynthesis, resting cell suspensions were incubated with supplemental L-arginine, and L-ornithine. 50mM Arginine was converted to a compound X that has low polarity. 50mM ornithine was not converted and remained in reaction solution. Compound X was purified using HPLC, and analyzed using (1)H-NMR and FAB-MS. These analyses showed that a compound X is "ornithine-lactam" (Mw＝114), which has a structure of circularized ornithine. These results indicated that S. incarnatus has an enzyme that converts arginine to ornithine-lactam. Such an enzyme has never been reported, and suggested that it may be relevant to sinefungin biosynthesis. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254　 98 1 2009 高度好熱性細菌 Thermus thermophilus HB8 由来アラニンラセマーゼの大腸菌での発現，精製及び諸性質の検討 1 7 EN Masahiko Yanagitani Satoshi Uemae Tomoyuki Shiraga Takashi Tamura Kenji Inagaki An alanine racemase (EC 5.1.1.1) from an extreme thermophilic bacterium Thermus thermophilus HB8, was purified and characterized, and its gene was cloned. The cloned alanine racemase gene (alr) was expressed in Escherichia coli JM 109. The alr gene is composed of a 1080 bp and encoded a 360 amino acid, and was predicted to have a molecular weight of 38,596. The enzyme was purified by heat shock at 70°C for 10min and DEAE Toyopearl 650M column chromatography. The purified enzyme had an optimum pH9.0∼10.0 and an optimum temperature of 55°C∼60°C. Enzyme activity was retained 100% after incubation of the enzyme at 70°C for 10min. Alanine racemase from Thermus thermophilus HB8 is a monomeric enzyme with a molecular mass of 39 kDa. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254　 97 1 2008 海産性好熱性細菌 Rhodothermus marinus 由来イソアミラーゼ の精製，性質検討及びＸ線結晶構造解析 1 7 EN Akiko Tachibana Takashi Tamura Katsumi Imada Miki Kinoshita Keiichi Namba Noriko Tsutsumi Miyoko Hashida Hiromichi Sakaguchi Kenji Inagaki The isoamylase gene from Rhodothermus marinus was cloned into and expressed in Escherichia coli Top 10. As a result of characterization of purified R. marinus isoamylase. the enzyme had an optimum pH of 4.0 and optimum temperature of 70℃. Thermal inactivation studies of the purified R. marinus isoamylase revealed the enzymatic activity to be uninfluenced after one hour incubation at 60℃. These results suggest that R. marinus isoamylase has high thermostability. The crystallization and crystal structure analysis of R. marinus isoamylase was performed. The three-dimensional structure at 1.9Å resolution was determined in complex with the panose. R. marinus isoamylase is composed of three domains N, A and C, and, has a (β/α)8-barrel in domain A. The secondary structural alignments of the R. marinus isoamylase and P. amyloderamosa isoamylase was carried out. They have the four active-site consensus regions characteristic of the α-amylase family. And the essential residue of the α-amylase family (D359, E395, and D467) was conserved in these enzymes. R. marinus isoamylase has shorter loops than P. amyloderamosa isoamylase. And R. marinus isoamylase had no Ca2+ binding site. These results are thought to be factors of thermostability of R. marinus isoamylase. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 85 1 1996 好熱性好酸性細菌の検索，単離および諸性質の検討 15 21 EN Yasuhide Tanimoto Kenji Inagaki Hidehiko Tanaka We have isolated 53 thermophilic and acidophilic bacteria from about 150 samples from acidic hot springs. All the strains isolated exhibited growth only at high temperatures and low pH ranges. We extensively characterized the strain UZ-1 which was isolated from Unzen spa. This strain was found to be a gram-negative, aerobic and heterotrophic bacterium. The DNA base composition was 63 mol% GC. Growth occurs over a range of 37℃ to 65℃ with an optimum temperature of 60℃, and between pH 2.0 and pH 6.0 with an optimum pH of 3.0. On the other hand, the optimum temperature of the other 6 isolated strains was 70℃. We report, in this paper, the characteristics of the isolated strains. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 86 1 1997 Alanine Racemase from an Acidophilic Bacterium, Acidiphilium organovorum 13 19 EN Teck Keong Seow Kenji Inagaki Takashi Tamura Hidehiko Tanaka Alanine racemase(EC 5.1.1.1)was screened from several acidophilic bacteria.Acidiphilium organovorum 13H showed the highest activity and was chosen as the representative source to study alaine racemase from acidphlic bacteria.The enzyme was found to be localised in the cytoplasm of the bacteria.Relative molecular mass syudies indicated that it had a dimeric native structure with identical subunits of about 34 kDa each.Maximum activity was observed between 50 and 60℃and at pH9.There was no loss of enzyme activity even after incubation at 65℃.The loss of activity upon dialysis against pyridoxal 5'-phosphate-free buffer containing hydroxylamine,and its partial recovery upon subsequent dialysis against buffer containing phyridoxal 5'-phosphate suggested that the enzyme required piridoxal 5'-phosphate as a co-factor for its catalytic activity. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 87 1 1998 Pseudomonas putida のＬ−メチオニン分解系オペロンの解析 53 58 EN Hiroyuki Inoue Takashi Tamura Kenji Inagaki Hidehiko Tanaka The mde operon and an upstream regulatory gene (mdeR) have been cloned and sequenced from Pseudomonas putida chromosomal DNA. The mde operon contains two structural genes involved in L-methionine degradative metabolism, which are mdeA (L-methionine γ-lyase gene) and mdeB (a gene encoding a homologous protein to the E1 component of pyruvate dehydrogenase complex). A rho-independent terminator was present just downstream of mdeB and open reading frames corresponding to other components of α-keto acid dehydrogenase complex were not found. When the mdeB gene product was overproduced in Escherichia coli, the E1 activity of the cell extract showed high specificity for α-ketobutyrate rather than pyruvate. these results suggest that mdeB encodes a novel E1 component, α-ketobutyrate dehydrogenase E1 component, and plays an important role in the metabolism of α-ketobutyrate produced by L-methionine γ-lyase from L-methionine. In addition,we found that mdeR gene was located on the opposite strand and began at 127 bp from the translational start site of mdeA. The mdeR gene product has been idetified as a member of the leucine responsive regulatory protein (Lrp) family and revealed to act as an essential positive regulator allowing the expression of the mdeAB operon. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 87 1 1998 染料脱色微生物の検索，単離及び脱色機構の解析 47 51 EN Kenji Inagaki Masakazu Kawaguchi Takaaki Taguchi Takashi Tamura Hidehiko Tanaka A yeast, Candida sp. MK-1, newly isolated from activated sludge as a dye decolorizing microorganism, decolorized Color lndex (C.l.) Reactive orange 16 and C.l. Reactive red 21 on the solid medium. Both azo dyes were also decolorized even in the liquid medium. The decolorizing activity by Candida sp. MK-1 depends on glucose concentration. Textile stained by Reactive orange 16 or Reactive red 21 was decolorized by Candida sp. MK-1. There results suggest that Candida sp. MK-1 has potential applications for the decolorization of textile and for the bioremediation of dye-contaminated wastewater. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 91 1 2002 Ｌ−グルタミン酸オキシダーゼを用いたグルタミン酸センサーの開発及びＧＯＴ/ＧＰＴセンシングへの応用 15 22 EN Jiro Arima Takashi Tamura Hiroaki Shinohara Hitoshi Kusakabe Hidehiko Tanaka Kenji Inagaki L-Glutamate measurement and GOT/GPT assay was successful by H2O2 measurement using the L-glutamate oxidase with 4-aminoantipyrine / phenol method. But, in examination of oxigen electrode, immobilized L-glutamate oxidase at the cellulose to L-glutamate and GOT-GPT sensor, Lpglutamate measurement was used for the amperometric determination with non-fixed enzyme. On examination of electron mediator, response for L-glutamate was observed with each of the compounds ferricyane, ferrocene-COOH, ferrocene-MeOH, and benzoquinone. L-Glutamate was measured by carbon printed tip electrode the L-glutamate oxidase and ferricyane based on the principle of chronoamperometry. A linear calibration graph was obtained between 1mM and 30mM. These results suggest that L-glutamate oxidase is able to utilize to L-glutamate sensor, and that there is a strong possibility to put this sensor to sensing for GOT/GPT activity. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 91 1 2002 好酸性細菌Acidocella Facilis由来菌体外酸性エステラーゼ遺伝子のクローニング 7 13 EN Tatsuya Takahashi Noboru Tanaka Takashi Tamura Chika Mukai Kimiyasu Isobe Norio Wakao Hidehiko Tanaka Kenji Inagaki An acidophilic heterotrophic bacterium, Acidocella facilis sp. AIU409 produces an extracellular acid esterase when grown in a medium containing sorbitan mono ester, Tween 80. The estA gene encoding for the acid esterase was isolated from the genomic library of A. facilis AIU409, cloned into Escherichia coli MV1184, and the nucleotide sequence of the gene was determined. The structural gene of estA was found to be 1881bp. The open reading frame of estA encodes 627 amino acid residues (calculated molecular mass, 64,140 daltons). A rho-independent terminator was present just downstream of the termination codon, TGA. The deduced N-terminal amino acid showed that the presursor of the acid esterase had a signal peptide composed of 23 amino acids and a consensus sequence of lipase, G-X-S-X-S. The molecular mass excluding the signal peptide calculated from the deduced amino acid sequence if the acid esterase is 61,846. This is lower than the molecular mass, 64kDa estimated by gel electrophoresis. The predicated amino acid sequence of the acid esterase has high similarity to the acyltransferase from Aeromonas hydrophila and the lipase from Xenorhadbus luminescens. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 91 1 2002 Improvement of Sinefungin-Producing Strain of Streptomyces incarnatus by Conferring Rifampicin-Resistance through Ultraviolet Light Irradiation and Protoplast Regeneration 1 5 EN Takashi Tamura Yin Shu Li Hidehiko Tanaka Kenji Inagaki Secondary metabolite production by gram-positive bacteria is strictly regulated at the transcription of the biosynthetic genes to mRNA in response to certain stringent conditions. Therefore, some mutational disruption of regulatory domains of the bacterial RNA polymerase might increase the production of the antibiotics. In this study, we have attempted to improve the sinefungin-producing strain of Streptomyces incarnatus NRRL 8057 by irradiating ultraviolet light on the protoplast, and selecting mutants that acquired the resistance to rifampicin, the antibiotic which specifically binds to the β-subunit of bacterial RNA polymerase. After three rounds of mutation, 10 strains were obtained with varied resistance to rifampicin. A mutant which showed the highest resistance was found to have the highest sinefungin production, which was 2.4 times higher(0.45±0.11μg/ml)than the wild type strain (0.19±0.07μg/ml). The breeding approach by rifampicin-resistance may be advantageous over the classical random screening since it requires much smaller number of candidates to be examined. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 92 1 2003 Semiempirical Molecular Orbital Calculation for the Redox Property of C-Terminal Active Site　Sequence of Human Thioredoxin Reductase 17 20 EN Takashi Tamura Hidehiko Tanaka Kenji Inagaki Semiempirical molecular orbital calculation (MOPAC) was used to estimate the enthalpy difference (ΔH) between the reduce and oxidized states of the C-terminal rebox center of human thioredoxin reductase. Heat of formation was computed by WinMOPAC 3.5Pro for the model peptides, N-Acetyl-Ser-Ile-Leu-Gly-X1-X2-Gly, whose-X1-X2-sequence was-Cys SeCys-(natural sequence), -SeCys-Cys-(reverse sequence), -Cys-Cys, and-SeCys-SeCys-. Calculation by Hamiltonian AM1 and PM3 agreed that the oxidized state with selenosulfide bonds and a diselenide bond were more favoralbe than their reduced states. Only the peptide that contained-Cys-Cys-sequence was shown to have lower enthalpy when the two Cys were in the reduced form. It has been reported that substitution of SeCys498 to Cys results in the mujtant TrxRs retaining only about 1% of the enzyme activity. The results of computational estimation supported the experimental hypothesis that the inactivation by SeCys498Cys mutation was due to the unfavorable formation of disulfide bond between Cys497-Cys498. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 92 1 2003 好酸性細菌Acidocella facilis 22Mの制限修飾系遺伝子のクローニングと塩基配列決定 9 15 EN Seiji Yamaoka Takashi Tamura Hisanori Takenobu Toshiyuki Kojo Hidehiko Tanaka Kenji Inagaki The gene encoding the Afa22MI restriction-modification system recognizing the sequence 5'-CGATCG-3' was cloned from Acidocella facilis 22M and sequenced. The cloned DNA fragment contained three genes encoding the Afa22MI methylase (M.Afa22MI) , the putative restriction endonuclease Afa22MI (R.Afa22MI) and a very short patch repair endonuclease (Afa22MI vsr) . M. Afa22MI gene has the conserved motifs of C5-cytosine methyltransferase. Afa22MI vsr gene was localized upstream of M. Afa22MI gene in opposite orientation, and an open reading frame of R. Afa22MI has about 53% sequence similarity to the amino acid sequence for the variable region of M.Xor�U. Afa22MI vsr has about 66% sequence similarity to the amino acid sequence of XorII vsr which was associated M. XorII. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 93 1 2004 Saccharomyces cerevisiae 由来 D-アミノ酸アセチルトランスフェラーゼの精製と性質 13 18 EN Yuriko Tashiro (Yamada) Takashi Tamura Hidehiko Tanaka Kenji Inagaki Some properties of D-amino scid acetyltransferase purified from Saccharomyces cerevisiae were investigated. The enzyme was purified to homogeneity by ammonium sulfate fractionation, column chromatographies on DEAE-Toyopearl 650M, Sephacryl S-200, QAE-Toyopearl 550C and affinity chromatography with D-glutamate as a ligand. The molecular weight was estimated to be about 53,000 by gel filtration. Relative molecular mass studies indicated that the enzyme was a monomer structure. The purified enzyme had an optimum pH of 8.4 and an optimum temperature of 40C. The Km values of the purified enzyme determined with tryptophan and acetyl-CoA were 4.5 * 10 -3M, respectively. The 20 residues of N-terminal amino acid sequence were analyzed. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254　 96 1 2007 The C-Terminal Tetrapeptide Sequence of Drosophila Thioredoxin Reductase Does not Function as a Redox-active Motif in the Human Lung Counterpart 1 5 EN Mitsuhiko Kuwahara Takashi Tamura Kentaro Kawamura Kenji Inagaki The isozymes of mammalian thioredoxin reductase (TrxR) contain the penultimate selenocysteineresidue (SeCys) in the redox-active C-terminal tetrapeptide, -Gly-Cys-SeCys-Gly (end). Amutant form of the mammalian enzyme TrxR-X498C in which SeCys is replaced with Cys showsa dramatically decreased catalytic activity, suggesting that SeCys residue plays an integral role inthe catalysis. In contrast, TrxR of the fruit fly, Drosophila melanogaster, has no selenium in the corresponding C-terminal redox sequence, which instead of SeCys has flanking serine residues in the terminal sequence, -Ser-Cys-Cys-Ser (end). Because the catalytic activity of Dm-TrxR is comparable to that of the mammalian selenoenzyme, we introduced the serine residues at the corresponding positions of the recombinant TrxR-X498C and mimicked the redox center of the fruit fly TrxR. However, the catalysis remained as low as the Cys mutant of the selenoenzyme, suggesting that the additional structural features are still required for the tetrapeptide to function as a redox center. MOPAC calculation suggested that the complete motif might involve the hexapeptide sequence, which includes a proline residue, -Pro-X-Ser-Cys-Cys-Ser (end). The proline-containing motif is conserved among other insect TrxRs such as those of honeybee and fruit fly. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 95 1 2006 染料脱色微生物による染料脱色機構の解析 1 5 EN Naoko Baba Hiromichi Sakaguchi Takaaki Taguchi Nobuki Hayase Takashi Tamura Kenji Inagaki The mehcanism of azo dyes decolorization by Candida sp. MK-1, Aeromonas sp. B-5 and Actinobacillus sp. B-11 were analyzed. The maximal decolorization activity was observed at pH 7.5 and 30℃ on Candida sp. MK-1, at alkaline and at 35℃ on Aeromonas sp. B-5 and Actinobacillus sp. B-11. The HPLC analysis of the supernatant of the Acid Red 27 detected in the blank. The retention time of this peak matched that of a reference standard compound of 4-amino-1-naphthalenesulfonate, produced by reductive cleavage of Acid Red 27. The decolorization of azo dyes with cell free extract of Candida sp. MK-a was promoted by the addition of several coenzymes or lawsone. The remarkable promotion of decolorization was observed by the addition of glutamate dehydrogenase with α-ketoglutarate and NH4+. Therefore, it was suggested that Candida sp. MK-1 azoreductase catalyzed decolorization of azo dye by NADPH dependent reductive cleavage. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 80 1 1992 Thiobacillus thiooxidansの固体平板培養法の改良とこの方法による新菌株の分離 37 43 EN Tatsuo Tano Mitsuru Harada Noriaki Kishimoto Kenji Inagaki Tsuyoshi Sugio Hidehiko Tanaka Thiobacillus thiooxidansは固体平板培地上でのコロニー形成が悪く,遺伝子操作を行うために欠かせない技術であるクローンの選抜が困難であったため,遺伝学的研究は従属細菌のそれに比して著しく遅れていた.本論文では,T.thiooxidansの個体平板培養法の改良を目的として,エネルギー源,ゲル化剤について検討し,得られた新しい固体培養法を用いて固体平板培地上で生育の速い菌株を分離した.新しい培地はSilvermanとLundgrenの9K培地の無機塩にエネルギー源として0.3% の四チオン酸,ゲル化剤として0.6% のジェランガムを用いた.分離株には,従属栄養生育能は認められなかったが,元素硫黄および四チオン酸を含む9K培地での良好な生育は確認できた.さらに,キノンがユビキノン8であり,菌体脂肪酸には3-ヒドロキシミリスチン酸が含まれること,GC含量が52% であること等の菌学的諸性質から分離株はT.thiooxidansに属する菌株であることが確認できた.この菌株と新しい平板培地を用いると,従属栄養細菌に匹敵する大型コロニーが得られ,細胞選抜を容易に行うことが出来る。 No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 80 1 1992 放線菌の産生するアミノアシラーゼ阻害剤の検索と単離同定,並びにその性質 25 30 EN Hidehiko Tanaka Kenji Inagaki アミノアシラーゼは固定化酵素として工業的に利用された最初の酵素であり,その応用面において精力的な研究がなされてきた.しかし,その生理学的及び酵素学的な面での研究はほとんど進展していない.本酵素の基礎面を研究する一つのアプローチとして,本酵素の阻害物質を放線菌を用いて検索し,2種の異なる阻害物質(�T,II)を見いだした.各種クロマトグラフィーにより阻害物質�Tを単一に精製し,機器分析にかけた結果,本物質はDL-乳酸であり,その阻害活性はL体にのみ認められた.各種α-ヒドロキシカルボン酸についてその阻害活性を検索したところ,DL-α-ヒドロキシ-n-酪酸,DL-α-ヒドロキシ-n-吉草酸,DL-α-ヒドロキシ-n-カプロン酸,L-β-フェニル乳酸が乳酸を上回る阻害活性を示した.最も強い阻害活性を示したDL-α-ヒドロキシ-n-カプロン酸のKiは約15μMでL-乳酸の0.9mMと比較すると,かなり低濃度で阻害を示すことが認められた.いずれの物質の阻害形式も基質に対して非拮抗的であった。 No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 94 1 2005 化学合成独立栄養細菌 Acidithiobacillus thiooxidans 由来アコニターゼの遺伝子解析と大腸菌での発現 1 7 EN Yohei Kanahara Takashi Tamura Chizuka Tokuda Atsuo Nakamura Hirokazu Matsukawa Kenji Inagaki An aconitase from Acidithiobacillus thiooxidans was purified and characterized, and its gene was cloned. The cloned aconitase gene (acn) was expressed in Escherichia coli JM 109; aconitase activity was found in the cell extarct. The acn gene encodes a 646-amino acid polypeptide and is located upstream of the isocitrate dehydrogenase gene (icd). A. thiooxidans aconitase showes high sequence similar to pig heart aconitase and E.coli aconitase B. Twenty-five of twenty-seven active site residues assigned in pig heart aconitase are conserved in A. thiooxidans aconitase. The enzyme was purified by DEAE-Toyopearl 650M column chromatogrophy. The purified enzyme had an optimum pH of 7.5 and an optimum temperature of 60 C. Thermal inactivation studies of the purified enzyme revealed the enzyme activity to be uninfluenced after one hour incubation at 40 c. Enzyme activity was retained 100% after incubation of the enzyme at pH 6.0-9.0 for 60min. The A. thiooxidans aconitase was composed of a single polypeptide chain with a molecular mass of 66 kDa. No potential conflict of interest relevant to this article was reported.