Biology:Betaine—homocysteine S-methyltransferase

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Short description: Class of enzymes
betaine-homocysteine S-methyltransferase
BHMT ribbon view.png
Crystal structure of rat liver betaine homocysteine s-methyltransferase.[1]
Identifiers
EC number2.1.1.5
CAS number9029-78-1
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

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]

  • Trimethylglycine (methyl donor) + homocysteine (hydrogen donor) → dimethylglycine (hydrogen receiver) + methionine (methyl receiver)
Diagram of the action of BHMT

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
4m3p.jpg
Betaine--homocysteine S-methyltransferase 1 homotetramer, Human
Identifiers
SymbolBHMT
NCBI gene635
HGNC1047
OMIM602888
RefSeqNM_001713
UniProtQ93088
Other data
EC number2.1.1.5
LocusChr. 5 q13.1-q15
betaine-homocysteine methyltransferase 2
Identifiers
SymbolBHMT2
NCBI gene23743
HGNC1048
OMIM605932
RefSeqNM_017614
UniProtQ9H2M3
Other data
EC number2.1.1.5
LocusChr. 5 q13

Tissue distribution

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.

See also

References

  1. PDB: 1UMY​; "Crystal structure of rat liver betaine homocysteine s-methyltransferase reveals new oligomerization features and conformational changes upon substrate binding". J. Mol. Biol. 338 (4): 771–82. May 2004. doi:10.1016/j.jmb.2004.03.005. PMID 15099744. 
  2. "Betaine homocysteine S-methyltransferase: just a regulator of homocysteine metabolism?". Cell. Mol. Life Sci. 63 (23): 2792–803. December 2006. doi:10.1007/s00018-006-6249-6. PMID 17086380. 
  3. Garrow TA (September 1996). "Purification, kinetic properties, and cDNA cloning of mammalian betaine-homocysteine methyltransferase". J. Biol. Chem. 271 (37): 22831–8. doi:10.1074/jbc.271.37.22831. PMID 8798461. 
  4. "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. doi:10.1006/abbi.1997.0246. PMID 9281325. 
  5. "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. doi:10.1006/geno.2000.6319. PMID 11087663. 
  6. "Betaine-homocysteine S-methyltransferase-2 is an S-methylmethionine-homocysteine methyltransferase". J. Biol. Chem. 283 (14): 8939–45. April 2008. doi:10.1074/jbc.M710449200. PMID 18230605. 
  7. "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. doi:10.1006/abbi.1997.0246. PMID 9281325. 

Further reading

  • "The synthesis of methionine by enzymic transmethylation. VII Existence of two separate homocysteine methylpherases on mammalian liver". Biochim. Biophys. Acta 54: 157–64. 1961. doi:10.1016/0006-3002(61)90948-9. PMID 14456704. 

External links