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:[2]
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[3][4] and BHMT2,[5][6] each encoded by a separate gene.
betaine-homocysteine methyltransferase
Betaine--homocysteine S-methyltransferase 1 homotetramer, Human
BHMT is expressed most predominantly in the liver and kidney.[7]
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.
^Sunden SL, Renduchintala MS, Park EI, Miklasz SD, Garrow TA (September 1997). "Betaine-homocysteine methyltransferase expression in porcine and human tissues and chromosomal localization of the human gene". Arch. Biochem. Biophys. 345 (1): 171–4.
doi:
10.1006/abbi.1997.0246.
PMID9281325.
^Chadwick LH, McCandless SE, Silverman GL, Schwartz S, Westaway D, Nadeau JH (November 2000). "Betaine-homocysteine methyltransferase-2: cDNA cloning, gene sequence, physical mapping, and expression of the human and mouse genes". Genomics. 70 (1): 66–73.
doi:
10.1006/geno.2000.6319.
PMID11087663.
^Sunden SL, Renduchintala MS, Park EI, Miklasz SD, Garrow TA (September 1997). "Betaine-homocysteine methyltransferase expression in porcine and human tissues and chromosomal localization of the human gene". Arch. Biochem. Biophys. 345 (1): 171–4.
doi:
10.1006/abbi.1997.0246.
PMID9281325.
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.
doi:
10.1016/0006-3002(61)90948-9.
PMID14456704.