title: Enzymology of H2S biogenesis, decay and signaling.
abstract: CONCLUSIONS
  Hydrogen sulfide (H2S), produced by the desulfuration of cysteine or homocysteine, functions as a signaling molecule in an array of physiological processes including regulation of vascular tone, the cellular stress response, apoptosis, and inflammation.
  
  
  BACKGROUND
  The low steady-state levels of H2S in mammalian cells have been recently shown to reflect a balance between its synthesis and its clearance. The subversion of enzymes in the cytoplasmic trans-sulfuration pathway for producing H2S from cysteine and/or homocysteine versus producing cysteine from homocysteine, presents an interesting regulatory problem.
  
  
  RESULTS
  It is not known under what conditions the enzymes operate in the canonical trans-sulfuration pathway and how their specificity is switched to catalyze the alternative H2S-producing reactions. Similarly, it is not known if and whether the mitochondrial enzymes, which oxidize sulfide and persulfide (or sulfane sulfur), are regulated to increase or decrease H2S or sulfane-sulfur pools.
  
  
  CONCLUSIONS
  In this review, we focus on the enzymology of H2S homeostasis and discuss H2S-based signaling via persulfidation and thionitrous acid.
authors.affiliation: Department of Biological Chemistry, University of Michigan Medical School , Ann Arbor, Michigan.
authors.forename: Omer
authors.initials: O
authors.lastname: Kabil
authors.forename: Ruma
authors.initials: R
authors.lastname: Banerjee
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D003541:Cystathionine beta-Synthase / Q000737:chemistry / Q000378:metabolism*; D003542:Cystathionine gamma-Lyase / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006862:Hydrogen Sulfide / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D010084:Oxidation-Reduction; D015398:Signal Transduction; D013440:Sulfides / Q000378:metabolism; D013466:Sulfurtransferases / Q000737:chemistry / Q000378:metabolism*
chemical_list: C483228:ETHE1 protein, human; D024101:Mitochondrial Proteins; D029543:Nucleocytoplasmic Transport Proteins; D013440:Sulfides; C051552:persulfides; D013466:Sulfurtransferases; C021550:3-mercaptopyruvate sulphurtransferase; D003541:Cystathionine beta-Synthase; D003542:Cystathionine gamma-Lyase; D006862:Hydrogen Sulfide