Cystathionine beta-synthase (IPR005857)

Short name: Cysta_beta_synth

Overlapping homologous superfamilies

Family relationships



Members of this family closely resemble cysteine synthase but contain an additional C-terminal CBS domain. Cysteine synthase (O-acetylserine (thiol)-lyase) is the enzyme responsible for the formation of cysteine from O-acetyl-serine and hydrogen sulphide with the concomitant release of acetic acid - the function of many of these enzymes is unproven.

This entry includes human CBS protein, which is a hydro-lyase catalyzing the first step of the transsulfuration pathway, where the hydroxyl group of L-serine is displaced by L-homocysteine in a beta-replacement reaction to form L-cystathionine, the precursor of L-cysteine. This catabolic route allows the elimination of L-methionine and the toxic metabolite L-homocysteine [PMID: 23981774, PMID: 20506325, PMID: 23974653]. Mutations in the CBS gene cause cystathionine beta-synthase deficiency (CBSD), an enzymatic deficiency resulting in altered sulfur metabolism and homocystinuria [PMID: 1301198, PMID: 20506325].

GO terms

Biological Process

GO:0019343 cysteine biosynthetic process via cystathionine

Molecular Function

GO:0004122 cystathionine beta-synthase activity

Cellular Component

GO:0005737 cytoplasm

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.