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Elucidating the Circuitry of the Human Hydrogen Sulfide Oxidation Pathway♦

Hydrogen sulfide is a ubiquitous signaling molecule that affects vascular tone, inflammation, and cell stress responses. It can also act as respiratory poison by reversibly inhibiting cytochrome c oxidase. To keep a handle on the useful and harmful effects of the molecule, cells need to maintain a steady-state concentration of hydrogen sulfide. However, the biochemical details of how cells control levels of hydrogen sulfide are not clear. In this Paper of the Week, Ruma Banerjee at the University of Michigan, Ann Arbor, and colleagues demonstrated that at physiologically relevant concentrations, the mitochondrial enzyme sulfide quinone oxidoreductase, which catalyzes the first step in hydrogen sulfide oxidation, uses glutathione as a persulfide acceptor. Glutathione persulfide is then utilized by the enzymes sulfur dioxygenase and rhodanese to make sulfite or thiosulfate. With this work, the authors present details about the sequence of reactions that takes place to keep the cell’s hydrogen sulfide concentration under control.