v5.1.0.3
Glycine data from LIS
Type | Family |
Description | 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; ) 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; ). 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 [ ]. Mammals utilise only cobalamin-dependent methionine synthase, while plants and yeasts utilise only the cobalamin-independent enzyme.This group represents cobalamin-independent methionine synthase [ ]. A group of archaeal proteins having substantial homology to the C-terminal region of this family is not included (see ). |
Short Name | Cobalamin-indep_Met_synthase |