EXPERIMENTAL VITAMIN B12 DEFICIENCY - ITS EFFECT ON TISSUE VITAMIN B12-COENZYME LEVELS AND ON METABOLISM OF METHYLMALONYL-COA

Vitamin B12-coenzyme levels have been measured in the liver, kidney, and brain of normal and vitamin B12-deficient rats, and in the liver, kidney, and heart of deficient and nondeficient pigs. In all cases, dietary restriction of vitamin B12 resulted in a decrease in coenzyme levels. In all cases the levels of coenzyme was significantly higher in rats than pigs. Methylmalonyl-CoA mutase activity was found in rat liver, brain, and kidney as well as in pig liver. In the livers of deficient animals this activity was significantly reduced. However, apoenzyme activity, i.e., isomerase activity measured in the presence of added vitamin B12-coenzyme, was increased approximately two-fold in the rat and four-fold in the most deficient pig. The ability of rat liver homogenates, deficient, and nondeficient, to catalyze hydrolysis of methylmalonyl-CoA was also demonstrated. A spectrophotometric assay for methylmalonyl-CoA is described. © 1969.