Figure 1.
H2S formation in cytosol as well as in mitochondria. The three enzymes CBS, CSE, and 3MST are responsible for H2S generation in cells. CBS and CSE are usually present in cytosol while 3MST is present in mitochondria. The sources of cytosolic H2S generation are l-methionine, homocysteine, cystathione, and l-cysteine. l-Cysteine also originates from a protein and cysteine and moreover also produces pyruvate and cystathione. In mitochondria, the source of H2S synthesis are mercaptopyruvate and l-cysteine. CBS, cystathionine β-synthase; 3MST, 3-mercaptopyruvate sulfurtransferase; CSE, cystathionine γ-lyase; α-KG, α-ketoglutarate; CAT, cysteine aminotransferase; H2S, hydrogen sulfide; TRX, thioredoxin.