EC 2.1.1.13 - Methionine synthase
IntEnz Enzyme Nomenclature
EC 2.1.1.13
Names
5-methyltetrahydrofolate—homocysteine transmethylase
N-methyltetrahydrofolate:L-homocysteine methyltransferase
N5-methyltetrahydrofolate methyltransferase
N5-methyltetrahydrofolate—homocysteine cobalamin methyltransferase
N5-methyltetrahydrofolic—homocysteine vitamin B12 transmethylase
B12 N5-methyltetrahydrofolate homocysteine methyltransferase
MetH
cobalamin-dependent methionine synthase
methionine synthase (cobalamin-dependent)
methionine synthetase
methyltetrahydrofolate—homocysteine vitamin B12 methyltransferase
tetrahydrofolate methyltransferase
tetrahydropteroylglutamate methyltransferase
tetrahydropteroylglutamic methyltransferase
vitamin B12 methyltransferase
Reaction
- 5-methyltetrahydrofolate + L-homocysteine = tetrahydrofolate + L-methionine
Cofactors
Comments:
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 1.16.1.8, [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 1.18.1.2, ferredoxin—NADP+ reductase). Acts on the monoglutamate as well as the triglutamate folate, in contrast with EC 2.1.1.14, 5-methyltetrahydropteroyltriglutamate—homocysteine S-methyltransferase, which acts only on the triglutamate.
Links to other databases
References
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The formation of methionine from the monoglutamate form of methyltetrahydrofolate by higher plants.Biochem. Biophys. Res. Commun. 36 : 228-234 (1969). [PMID: 5799642]
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Cobalamin and the synthesis of methionine by Escherichia coli.Nature 201 : 39-42 (1964).
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Transfer of the methyl group from N5-methyltetrahydrofolates to homocysteine in Escherichia coli.Biochem. J. 92 : 497-504 (1964).
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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).
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Escherichia coli B N5-methyltetrahydrofolate-homocysteine cobalamin methyltransferase: gel-filtration behavior of apoenzyme and holoenzymes.Biochim. Biophys. Acta 242 : 355-364 (1971). [PMID: 4946148]
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Methionine synthase exists in two distinct conformations that differ in reactivity toward methyltetrahydrofolate, adenosylmethionine, and flavodoxin.Biochemistry 37 : 5372-5382 (1998). [PMID: 9548919]
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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).
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Interaction of flavodoxin with cobalamin-dependent methionine synthase.Biochemistry 39 : 10711-10719 (2000). [PMID: 10978155]
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Domain alternation switches B12-dependent methionine synthase to the activation conformation.Nat. Struct. Biol. 9 : 53-56 (2002). [PMID: 11731805]
[EC 2.1.1.13 created 1972, modified 2003]