Epithelial Electrolyte Transport Physiology and the Gasotransmitter Hydrogen Sulfide
Sources of hydrogen sulfide. (a) Environmental hydrogen sulfide (H2S) occurs due to geothermal activities such as volcanoes, sulfur deposits, or sulfur springs. The pictures show the Halema‘uma‘u crater (top) and sulfur deposit (bottom) on Hawaii Big Island. (b) Microbial production of H2S. Sulfate-reducing bacteria dissimilate sulfate into H2S via dissimilatory sulfite reductase (DSR). Mesophilic bacteria use orthologues of the mammalian H2S-generating enzymes cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3MST) in order to generate H2S from cysteine. (c) Mammalian cells produce H2S from cysteine via CBS, CSE, and 3MST (1). H2S can be stored in a reductant-labile intracellular pool as bound sulfane sulfur (2). The degradation of H2S occurs via oxidative metabolic pathways in mitochondria (3).