EC 18.104.22.168 - Methionine synthase
IntEnz Enzyme Nomenclature
N5-methyltetrahydrofolate—homocysteine cobalamin methyltransferase
N5-methyltetrahydrofolic—homocysteine vitamin B12 transmethylase
B12 N5-methyltetrahydrofolate homocysteine methyltransferase
cobalamin-dependent methionine synthase
methionine synthase (cobalamin-dependent)
methyltetrahydrofolate—homocysteine vitamin B12 methyltransferase
vitamin B12 methyltransferase
11175 [IUBMB](6S)-5-methyl-5,6,7,8-tetrahydrofolate(6S)-5-methyl-5,6,7,8-tetrahydrofolateName origin: UniProt - CHECKED (C)Formula: C20H23N7O6
Charge: -2ChEBI compound status: CHECKED (C)L-homocysteineL-homocysteineName origin: UniProt - CHECKED (C)Formula: C4H9NO2S
Charge: 0ChEBI compound status: CHECKED (C)<=>(6S)-5,6,7,8-tetrahydrofolate(6S)-5,6,7,8-tetrahydrofolateName origin: UniProt - CHECKED (C)Formula: C19H21N7O6
Charge: -2ChEBI compound status: CHECKED (C)
Contains zinc and cobamide. The enzyme becomes inactivated occasionally during its cycle by oxidation of Co(I) to Co(II). Reactivation by reductive methylation is catalysed by the enzyme itself, with S-adenosyl-L-methionine as the methyl donor and a reducing system. For the mammalian enzyme, the reducing system involves NADPH and EC 22.214.171.124, [methionine synthase] reductase. In bacteria, the reducing agent is flavodoxin, and no further catalyst is needed (the flavodoxin is kept in the reduced state by NADPH and EC 126.96.36.199, ferredoxin—NADP+ reductase). Acts on the monoglutamate as well as the triglutamate folate, in contrast with EC 188.8.131.52, 5-methyltetrahydropteroyltriglutamate—homocysteine S-methyltransferase, which acts only on the triglutamate.
Links to other databases
The formation of methionine from the monoglutamate form of methyltetrahydrofolate by higher plants.Biochem. Biophys. Res. Commun. 36: 228-234 (1969). [PMID: 5799642]
Cobalamin and the synthesis of methionine by Escherichia coli.Nature 201: 39-42 (1964).
Transfer of the methyl group from N5-methyltetrahydrofolates to homocysteine in Escherichia coli.Biochem. J. 92: 497-504 (1964).
Enzymatic synthesis of the methyl group of methionine. VII. Isolation of a cobalamin-containing transmethylase (5-methyltetrahydro-folate-homocysteine) from mammalian liver.J. Biol. Chem. 239: 2888-2895 (1964).
Escherichia coli B N5-methyltetrahydrofolate-homocysteine cobalamin methyltransferase: gel-filtration behavior of apoenzyme and holoenzymes.Biochim. Biophys. Acta 242: 355-364 (1971). [PMID: 4946148]
Methionine synthase exists in two distinct conformations that differ in reactivity toward methyltetrahydrofolate, adenosylmethionine, and flavodoxin.Biochemistry 37: 5372-5382 (1998). [PMID: 9548919]
Characterization of the zinc binding site in methionine synthase enzymes of Escherichia coli: The role of zinc in the methylation of homocysteine.J. Am. Chem. Soc. 120: 8410-8416 (1998).
Interaction of flavodoxin with cobalamin-dependent methionine synthase.Biochemistry 39: 10711-10719 (2000). [PMID: 10978155]
Domain alternation switches B12-dependent methionine synthase to the activation conformation.Nat. Struct. Biol. 9: 53-56 (2002). [PMID: 11731805]
[EC 184.108.40.206 created 1972, modified 2003]