Betaine—homocysteine S-methyltransferase

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

betaine-homocysteine S-methyltransferase
Crystal structure of rat liver betaine homocysteine s-methyltransferase.[1]
Identifiers
EC no.	2.1.1.5
CAS no.	9029-78-1
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / QuickGO
Search PMC articles PubMed articles NCBI proteins

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 Identifiers Symbol BHMT NCBI gene 635 HGNC 1047 OMIM 602888 RefSeq NM_001713 UniProt Q93088 Other data EC number 2.1.1.5 Locus Chr. 5 q13.1-q15 Search for Structures Swiss-model Domains InterPro

betaine-homocysteine methyltransferase 2 Identifiers Symbol BHMT2 NCBI gene 23743 HGNC 1048 OMIM 605932 RefSeq NM_017614 UniProt Q9H2M3 Other data EC number 2.1.1.5 Locus Chr. 5 q13 Search for Structures Swiss-model Domains InterPro

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

• Betaine