The Mechanisms of the Choline Oxidase and Transmethylase Enzyme Systems.

Abstract

The mechanisms of choline and betaine aldehyde conversion to betaine and methyl group transfer to homocysteine were investigated both in aerobic and anaerobic systems. The expected yield of acid groups, assumed to be betaine, from oxidation of choline and betaine aldehyde is only half of the theoretical value. Betaine aldehyde appears to be metabolized by 2 pathways, one an aerobic oxidation and the other an anaerobic conversion to betaine. Choline, betaine aldehyde, and betaine are equivalent methyl group donors to homocysteine under aerobic conditions. Anaerobically choline is almost inactive in furnishing methyl groups to homocysteine. Betaine, however, is a more active methyl donor anaerobically than under aerobic conditions.