Betaine—homocysteine S-methyltransferase explained

betaine-homocysteine S-methyltransferase
Ec Number:	2.1.1.5
Cas Number:	9029-78-1
Go Code:	0047150

In the field of enzymology, a betaine-homocysteine S-methyltransferase also known as betaine-homocysteine methyltransferase (BHMT) is a zinc metallo-enzyme that catalyzes the transfer of a methyl group from trimethylglycine and a hydrogen ion from homocysteine to produce dimethylglycine and methionine respectively:^[1]

• Trimethylglycine (methyl donor) + homocysteine (hydrogen donor) → dimethylglycine (hydrogen receiver) + methionine (methyl receiver)

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. This enzyme participates in the metabolism of glycine, serine, threonine and also methionine.

Isozymes

In humans, there are two isozymes, BHMT^{[2] [3]} and BHMT2,^{[4] [5]} each encoded by a separate gene.

betaine-homocysteine methyltransferase Caption: Betaine--homocysteine S-methyltransferase 1 homotetramer, Human Width: 270 Hgncid: 1047 Symbol: BHMT Entrezgene: 635 Omim: 602888 Refseq: NM_001713 Uniprot: Q93088 Ecnumber: 2.1.1.5 Chromosome: 5 Arm: q Band: 13.1 Locussupplementarydata: -q15

betaine-homocysteine methyltransferase 2 Hgncid: 1048 Symbol: BHMT2 Entrezgene: 23743 Omim: 605932 Refseq: NM_017614 Uniprot: Q9H2M3 Ecnumber: 2.1.1.5 Chromosome: 5 Arm: q Band: 13

Tissue distribution

BHMT is expressed most predominantly in the liver and kidney.^[6]

Clinical significance

Mutations in the BHMT gene are known to exist in humans. Anomalies may influence the metabolism of homocysteine, which is implicated in disorders ranging from vascular disease, autism, and schizophrenia to neural tube birth defects such as spina bifida.

See also

• Betaine

Further reading

• Klee WA, Richards HH, Cantoni GL . 1961 . The synthesis of methionine by enzymic transmethylation. VII Existence of two separate homocysteine methylpherases on mammalian liver . Biochim. Biophys. Acta . 54 . 157 - 64 . 14456704 . 10.1016/0006-3002(61)90948-9 .

Notes and References

1. Pajares MA, Pérez-Sala D . Betaine homocysteine S-methyltransferase: just a regulator of homocysteine metabolism? . Cell. Mol. Life Sci. . 63 . 23 . 2792–803 . December 2006 . 17086380 . 10.1007/s00018-006-6249-6 . 10261/13799 . 6076708 . free .
2. Garrow TA . Purification, kinetic properties, and cDNA cloning of mammalian betaine-homocysteine methyltransferase . J. Biol. Chem. . 271 . 37 . 22831–8 . September 1996 . 8798461 . 10.1074/jbc.271.37.22831. free.
3. Sunden SL, Renduchintala MS, Park EI, Miklasz SD, Garrow TA . Betaine-homocysteine methyltransferase expression in porcine and human tissues and chromosomal localization of the human gene . Arch. Biochem. Biophys. . 345 . 1 . 171–4 . September 1997 . 9281325 . 10.1006/abbi.1997.0246 .
4. Chadwick LH, McCandless SE, Silverman GL, Schwartz S, Westaway D, Nadeau JH . Betaine-homocysteine methyltransferase-2: cDNA cloning, gene sequence, physical mapping, and expression of the human and mouse genes . Genomics . 70 . 1 . 66–73 . November 2000 . 11087663 . 10.1006/geno.2000.6319 .
5. Szegedi SS, Castro CC, Koutmos M, Garrow TA . Betaine-homocysteine S-methyltransferase-2 is an S-methylmethionine-homocysteine methyltransferase . J. Biol. Chem. . 283 . 14 . 8939–45 . April 2008 . 18230605 . 10.1074/jbc.M710449200 . 2276374 . free .
6. Sunden SL, Renduchintala MS, Park EI, Miklasz SD, Garrow TA . Betaine-homocysteine methyltransferase expression in porcine and human tissues and chromosomal localization of the human gene . Arch. Biochem. Biophys. . 345 . 1 . 171–4 . September 1997 . 9281325 . 10.1006/abbi.1997.0246 .