Cystathionine beta-synthase and cystathionine gamma-lyase (CBS and CSE (or CGL for cystathionine gamma-lyase, also sometimes referred to as CBL for cystathionine beta-lyase; the most accepted abbreviations in mammals are CBS for cystathionine beta-synthase and CSE for cystathionine gamma-lyase)[2][4])

Cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CSE, or CGL) are two pyridoxal phosphate-dependent enzymes that catalyze sequential steps in the transsulfuration pathway, converting homocysteine to cystathionine (CBS) and then cystathionine to cysteine (CSE)[2][3][4]. Both enzymes are key regulators of sulfur-containing amino acid metabolism, critically involved in cellular redox regulation, detoxification of homocysteine, and endogenous production of hydrogen sulfide (H₂S), an important physiological gasotransmitter[3][4]. Deficiencies or dysfunctions contribute to cardiovascular, neurological, and metabolic disorders. CBS is linked to homocystinuria, while CSE deficiency is associated with cystathioninuria, elevated cardiovascular risk, and altered redox balance[2][4][5]. Both enzymes are emerging therapeutic and diagnostic targets, and their activities or expression levels serve as potential biomarkers for various metabolic and vascular diseases[2][4][5].

Other names

CBSβ-thionasecysteine synthaseL-serine hydro-lyase (adding homocysteine)methylcysteine synthaseserine sulfhydraseserine sulfhydrylaseCSECGLcystathionaseβ-cystathionasecystathionine beta-lyase (CBL: a common bacterial and yeast synonym)L-cystathionine L-homocysteine-lyase (deaminating; pyruvate-forming)

CBS and CSE inhibitors: reduce hydrogen sulfide (H₂S) synthesis, alter cysteine biosynthesis, raise homocysteine levels Betaine: enhances homocysteine remethylation when CBS is deficient Pyridoxine: improves CBS enzyme activity (if the enzyme is responsive to B6) Experimental CBS inhibitors: used as potential antimicrobial agents (target bacterial/yeast CBL)