Abstract
FOR the biosynthesis of choline, Jukes (1947) and Artom (1952) proposed a scheme for the stepwise addition of methyl groups from methionine via transmethylation to aminoethanol. However, Stekol et al. (1955) demonstrated that dimethylaminoethanol was the only direct acceptor of the methyl group of methionine for choline biosynthesis in rats, the other 2 methyl groups were produced by de novo synthesis involving folic acid. Stekol (1958) postulated the following stepwise sequence for choline biosynthesis:The de novo synthesis of methyl groups was supported by studies of Nyc (1956) in a mutant strain of Neurospora crassa where formate-C14 was incorporated far in excess than C14H3 of methionine into methylaminoethanol. Young el al. (1955) found that choline requirement of chickens was decreased by dietary folic acid. Also, choline could be replaced by an equimolar quantity of monomethylaminoethanol plus betaine, either in presence or absence of folic acid. Vitamin B12 spared choline requirements …
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