Figure 1.

Metabolism of sulfur containing amino acids. (a) Homocysteine-dependent transsulfuration pathway that containing both cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE). Which is located in the cytosol and generates hydrogen sulfide (H₂S). (b) H₂S synthesis via aspartate aminotransferase (AAT) and 3-mercaptopyruvate sulfurtransferase (3MST), which occurs in the cytosol and mitochondria. (c) Catabolism of cysteine via cysteine dioxygenase (CDO) and AAT generates sulfur dioxide (SO₂).