Fig. 1
From: Homocysteine, B vitamins, and cardiovascular disease: a Mendelian randomization study
Overview of folate, vitamin B6, and vitamin B12 in homocysteine metabolism. Homocysteine is reconverted to methionine by receiving a methyl group from 5-methyltetrahydrofolate, the active form of folate, or betaine in the remethylation pathway. Irreversible removal of homocysteine occurs through the transsulphuration pathway where homocysteine condenses with serine to form cystathionine