CBS

The protein encoded by this gene acts as a homotetramer to catalyze the conversion of homocysteine to cystathionine, the first step in the transsulfuration pathway. The encoded protein is allosterically activated by adenosyl-methionine and uses pyridoxal phosphate as a cofactor. Defects in this gene can cause cystathionine beta-synthase deficiency (CBSD), which can lead to homocystinuria. This gene is a major contributor to cellular hydrogen sulfide production. Multiple alternatively spliced transcript variants have been found for this gene. [provided by RefSeq, Feb 2016]

Cystathionine-Beta-Synthase

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 (PubMed:23981774, PubMed:20506325, PubMed:23974653).
Also involved in the production of hydrogen sulfide, a gasotransmitter with signaling and cytoprotective effects on neurons (By similarity).

Cysteine biosynthetic process Source: BHF-UCL
Cysteine biosynthetic process from serine Source: InterPro
Cysteine biosynthetic process via cystathionine Source: InterPro
DNA protection Source: BHF-UCL
Homocysteine catabolic process Source: UniProtKB
Homocysteine metabolic process Source: UniProtKB
Hydrogen sulfide biosynthetic process Source: UniProtKB
L-cysteine catabolic process Source: UniProtKB
L-serine catabolic process Source: UniProtKB
L-serine metabolic process Source: UniProtKB
Transsulfuration Source: GO_Central

Cytoplasm; Nucleus

Cystathionine beta-synthase deficiency (CBSD): An enzymatic deficiency resulting in altered sulfur metabolism and homocystinuria. The clinical features of untreated homocystinuria due to CBS deficiency include myopia, ectopia lentis, mental retardation, skeletal anomalies resembling Marfan syndrome, and thromboembolic events. Light skin and hair can also be present. Biochemical features include increased urinary homocystine and methionine.