5-Methyltetrahydropteroyltriglutamate—homocysteine S-methyltransferase explained
In enzymology, a 5-methyltetrahydropteroyltriglutamate—homocysteine S-methyltransferase is an enzyme that catalyzes the chemical reaction
5-methyltetrahydropteroyltri-L-glutamate + L-homocysteine
tetrahydropteroyltri-L-glutamate + L-methionine
Thus, 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 participates in methionine metabolism. It has 2 cofactors: orthophosphate, and zinc.
Nomenclature
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.
Structure
The enzyme from Escherichia coli consists of two alpha8-beta8 (TIM) barrels positioned face to face and thought to have evolved by gene duplication.[1] 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 .
Further reading
- Guest JR, Friedman S, Foster MA, Tejerina G, Woods DD . Transfer of the methyl group from N5-methyltetrahydrofolates to homocysteine in Escherichia coli . The Biochemical Journal . 92 . 3 . 497–504 . September 1964 . 10.1042/bj0920497 . 5319972 . 1206090 . Free full text .
- Whitfield CD, Steers EJ, Weissbach H . Purification and properties of 5-methyltetrahydropteroyltriglutamate-homocysteine transmethylase . The Journal of Biological Chemistry . 245 . 2 . 390–401 . January 1970 . 10.1016/S0021-9258(18)63404-0 . 4904482 . Free full text . free .
- Eichel J, González JC, Hotze M, Matthews RG, Schröder J . Vitamin-B12-independent methionine synthase from a higher plant (Catharanthus roseus). Molecular characterization, regulation, heterologous expression, and enzyme properties . European Journal of Biochemistry . 230 . 3 . 1053–8 . June 1995 . 7601135 . 10.1111/j.1432-1033.1995.tb20655.x . https://archive.today/20130105123612/http://www3.interscience.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0014-2956&date=1995&volume=230&issue=3&spage=1053 . dead . 2013-01-05 . Free full text .
- González JC, Peariso K, Penner-Hahn JE, Matthews RG . Cobalamin-independent methionine synthase from Escherichia coli: a zinc metalloenzyme . Biochemistry . 35 . 38 . 12228–34 . September 1996 . 8823155 . 10.1021/bi9615452 . James Penner-Hahn .
- Peariso . Katrina . 1998 . 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 . 10.1021/ja980581g . Goulding . Celia W. . Huang . Sha . Matthews . Rowena G. . Penner-Hahn . James E. . 33 . James Penner-Hahn . vanc .
Notes and References
- Pejchal R, Ludwig ML . Cobalamin-independent methionine synthase (MetE): a face-to-face double barrel that evolved by gene duplication . PLOS Biology . 3 . 2 . e31 . February 2005 . 15630480 . 539065 . 10.1371/journal.pbio.0030031 . free .
