When the crystalline beef liver catalase was treated with SDS (sodium n-dodecyl sulfate) or LIS (3, 5-diiodosalicylic acid lithium salt) which is a kind of the anionic surfactant, its catalase activity dwindled and disappeared at last, and its peroxidatic activity was exhibited. It was found by the ultracentrifugal analysis that the molecule of beef liver catalase treated with SDS splited into two subunits with sedimentation constants of about 10S and 2S. The same phenomena as mentioned above were compared in the crude catalase extracts of livers from normal mice and acatalasemia mice. In the crude catalase extracts from both mice, catalase activities dwindled and disappeared in the same way and peroxidatic activities appeared if treated with SDS. But peroxidatic activity of acatalasemia liver extract was higher than that of normal liver extract. It seems that the liver catalase in acatalasemia mouse is more labile by SDS treatment than that in normal mouse, resulting in showing the conformational changes of catalase molecule in acatalasemia mouse liver.