Cobalamin-independent methionine synthase (IPR006276)

Short name: Cobalamin-indep_Met_synthase

Overlapping homologous superfamilies

Family relationships



Methionine synthases catalyse the the final step of methionine biosynthesis. Two apparently unrelated families of proteins catalyse this step: cobalamin-dependent methionine synthase, which catalyses the transfer of a methyl group from N5-methyltetrahydrofolate to L-homocysteine and requires cobalamin as a cofactor (MetH; 5-methyltetrahydrofolate:L-homocysteine S-methyltransferase; EC: and cobalamin-independent methionine synthase, which catalyses the transfer of a methyl group from methyltetrahydrofolate to L-homocysteine without using an intermediate methyl carrier (MetE; 5-methyltetrahydropteroyltri-L-glutamate:L-homocysteine S-methyltransferase; EC: These enzymes display no detectable sequence homology between them, but both require zinc for activation and binding to L-homocysteine. Organisms that cannot obtain cobalamin (vitamin B12) encode only the cobalamin-independent enzyme. Escherichia coli and many other bacteria express both enzymes [PMID: 1339288]. Mammals utilise only cobalamin-dependent methionine synthase, while plants and yeasts utilise only the cobalamin-independent enzyme.

This group represents cobalamin-independent methionine synthase [PMID: 15630480]. A group of archaeal proteins having substantial homology to the C-terminal region of this family is not included (see IPR002629).

GO terms

Biological Process

GO:0009086 methionine biosynthetic process

Molecular Function

GO:0003871 5-methyltetrahydropteroyltriglutamate-homocysteine S-methyltransferase activity
GO:0008270 zinc ion binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.