EC number 2.1.1.14 IntEnz IntEnz view ExPASy NiceZyme view | CAS number 9068-29-5 BRENDA BRENDA entry KEGG KEGG entry | |
In enzymology, a 5-methyltetrahydropteroyltriglutamate—homocysteine S-methyltransferase (EC 2.1.1.14) is an enzyme that catalyzes the chemical reaction
5-methyltetrahydropteroyltri-L-glutamate + L-homocysteineThus, the two substrates of this enzyme are 5-methyltetrahydropteroyltri-L-glutamate and L-homocysteine, whereas its two products are tetrahydropteroyltri-L-glutamate and L-methionine.
This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is 5-methyltetrahydropteroyltri-L-glutamate:L-homocysteine S-methyltransferase. Other names in common use include tetrahydropteroyltriglutamate methyltransferase, homocysteine methylase, methyltransferase, tetrahydropteroylglutamate-homocysteine transmethylase, methyltetrahydropteroylpolyglutamate:homocysteine methyltransferase, cobalamin-independent methionine synthase, methionine synthase (cobalamin-independent), and MetE. This enzyme participates in methionine metabolism. It has 2 cofactors: orthophosphate, and zinc.
Structural studies
As of late 2007, 9 structures have been solved for this class of enzymes, with PDB accession codes 1T7L, 1U1H, 1U1J, 1U1U, 1U22, 1XDJ, 1XPG, 1XR2, and 2NQ5. The enzyme from Escherichia coli consists of two alpha8-beta8 (TIM) barrels positioned face to face and thought to have evolved by gene duplication. The active site lies between the tops of the two barrels, the N-terminal barrel binds 5-methyltetrahydropteroyltri-L-glutamic acid and the C-terminal barrel binds homocysteine. Homocysteine is coordinated to a zinc ion, as initially suggested by spectroscopy and mutagenesis .