In enzymology, a cystathionine beta-lyase (EC 18.104.22.168) is an enzyme that catalyzes the chemical reaction
- L-cystathionine + H2O L-homocysteine + NH3 + pyruvate
Thus, the two substrates of this enzyme are L-cystathionine and H2O, whereas its 3 products are L-homocysteine, NH3, and pyruvate.
This enzyme belongs to the family of lyases, specifically the class of carbon-sulfur lyases. The systematic name of this enzyme class is L-cystathionine L-homocysteine-lyase (deaminating; pyruvate-forming). Other names in common use include beta-cystathionase, cystine lyase, cystathionine L-homocysteine-lyase (deaminating), and L-cystathionine L-homocysteine-lyase (deaminating). This enzyme participates in 5 metabolic pathways: methionine metabolism, cysteine metabolism, selenoamino acid metabolism, nitrogen metabolism, and sulfur metabolism. It employs one cofactor, pyridoxal phosphate.
As of late 2007, 5 structures have been solved for this class of enzymes, with PDB accession codes 1CL1, 1CL2, 1IBJ, 2FQ6, and 2GQN.