ENZYME entry: EC 2.1.1.13

Accepted Name
Methionine synthase.
Alternative Name(s)
5-methyltetrahydrofolate--homocysteine S-methyltransferase.
5-methyltetrahydrofolate--homocysteine transmethylase.
B12 N(5)-methyltetrahydrofolate homocysteine methyltransferase.
Cobalamin-dependent methionine synthase.
Methionine synthase (cobalamin-dependent).
Methionine synthetase.
Methyltetrahydrofolate--homocysteine vitamin B12 methyltransferase.
N(5)-methyltetrahydrofolate methyltransferase.
N(5)-methyltetrahydrofolate--homocysteine cobalamin methyltransferase.
N(5)-methyltetrahydrofolic--homocysteine vitamin B12 transmethylase.
N-methyltetrahydrofolate:L-homocysteine methyltransferase.
Tetrahydrofolate methyltransferase.
Tetrahydropteroylglutamate methyltransferase.
Tetrahydropteroylglutamic methyltransferase.
Vitamin B12 methyltransferase.
Reaction catalysed
5-methyltetrahydrofolate + L-homocysteine <=> tetrahydrofolate + L-methionine
Cofactor(s)
Cob(II)alamin; Zn(2+).
Comment(s)
  • The enzyme becomes inactivated occasionally during its cycle by oxidation of Co(I) to Co(II).
  • Reactivation by reductive methylation is catalyzed 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.
  • 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).
  • Acts on the monoglutamate as well as the triglutamate folate, in contrast with EC 2.1.1.14, which acts only on the triglutamate.
Cross-references
PROSITEPDOC50972
BRENDA2.1.1.13
EC2PDB2.1.1.13
ExplorEnz2.1.1.13
PRIAM enzyme-specific profiles2.1.1.13
KEGG Ligand Database for Enzyme Nomenclature2.1.1.13
IUBMB Enzyme Nomenclature2.1.1.13
IntEnz2.1.1.13
MEDLINEFind literature relating to 2.1.1.13
MetaCyc2.1.1.13
UniProtKB/Swiss-Prot
Q9AJQ8, METH_ALIFS;  Q4JIJ3, METH_BOVIN;  A8XY95, METH_CAEBR;  
Q09582, METH_CAEEL;  Q54P92, METH_DICDI;  P13009, METH_ECOLI;  
Q99707, METH_HUMAN;  A6H5Y3, METH_MOUSE;  Q49775, METH_MYCLE;  
O33259, METH_MYCTU;  Q9I2Q2, METH_PSEAE;  O33465, METH_PSEPU;  
Q9Z2Q4, METH_RAT;  P37586, METH_SALTY;  Q55786, METH_SYNY3;  
Q9KUW9, METH_VIBCH;  Q5E814, METH_VIBF1;  Q87L95, METH_VIBPA;  
Q8DCJ7, METH_VIBVU;  Q7MHB1, METH_VIBVY;  

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