Possible interrelationship between vitamins E and b12 in the disturbance in methylmalonate metabolism in vitamin E deficiency.

1. The disturbance in 2-methylmalonate metabolism resulting in its increased urinary excretion observed in vitamin E deficiency is not caused by increased formation of methylmalonate from propionate as is evident from the activity of the enzyme propionyl-CoA carboxylase (EC 6.4.1.3), but can be traced to an impairment in the conversion of methylmalonate into succinate by the vitamin B12-requiring enzyme, methylmalonyl-CoA mutase (EC 5.4.99.2) in rat liver. 2. It is shown that the decrease in the activity of methylmalonyl-CoA mutase in vitamin E deficiency is not a consequence of a secondary vitamin B12 deficiency. Peroxidative destruction of the coenzyme in vitamin E deficiency was also ruled out. The results suggest a defect in the conversion of cyanocobalamin into its coenzyme form.