has part has part characteristic of inheres in has modifier L-methionine metabolic process Decreased methionine synthase activity A reduction in methionine synthase activity. Decreased activity of methionine synthase Methionine synthase deficiency UMLS:C1848580 HP:0003524 Cobalamin-dependent methionine synthase catalyzes the transfer of a methyl group from N5-methyltetrahydrofolate to homocysteine, producing tetrahydrofolate and methionine, i.e., (6S)-5-methyl-5,6,7,8-tetrahydrofolate + L-homocysteine = (6S)-5,6,7,8-tetrahydrofolate + L-methionine. Reduced methionine synthase activity Methionine synthase activity decreased Abnormal circulating enzyme concentration or activity abnormal decreased process quality