MAMMALIAN METHYLMALONYL ISOMERASE AND VITAMIN B 12 COENZYMES

Abstract
Methylmalonyl isomerase apoenzyme was prepared from sheep kidney cortex enzyme fractions by acidification in the presence of ammonium sulfate. Activity was restored by dimethylben-zimidazolyl- and benzimidazolycobamide coenzymes but adenylcobamide coenzyme had little or no effect. In contrast, the 3 coenzymes were active with methylmalonyl isomerase preparations from Propioni-bacterium shermanii. A study of the effects of illumination, charcoal treatment and incubation with intrinsic factor on the native and the cobamide coenzyme-reactivated kidney enzyme, suggested that the strength of the apoenzyme-coenzyme binding in this enzyme is greater before than after resolution.