Biosynthesis and metabolism of H2S

Figure 17: H₂S is synthesized from the sulfur containing amino acid, L-cysteine by cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) with cysteine aminotransferase (CAT). CBS is expressed in brain, liver, kidney, ileum, placenta and pancreatic islets, whereas CSE predominates in the cardiovascular system, especially the myocardium and vascular smooth muscle cells. CAT and 3-MST are both expressed in the brain and vascular endothelium. 3-MST produces H₂S from 3-MP which produced by CAT from L-cysteine and α-ketoglutarate