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Human sulfide:quinone oxidoreductase catalyzes the first step in hydrogen sulfide metabolism and produces a sulfane sulfur metabolite
Journal article   Peer reviewed

Human sulfide:quinone oxidoreductase catalyzes the first step in hydrogen sulfide metabolism and produces a sulfane sulfur metabolite

Michael R Jackson, Scott L Melideo and Marilyn Schuman Jorns
Biochemistry (Easton), v 51(34), pp 6804-6815
28 Aug 2012
DOI: https://doi.org/10.1021/bi300778t
PMID: 22852582
Featured in Collection :   UN Sustainable Development Goals @ Drexel

Abstract

Hydrogen Sulfide - metabolism Quinone Reductases - chemistry Quinone Reductases - metabolism Sulfur - metabolism Biocatalysis Humans Quinone Reductases - genetics Kinetics Hydrogen-Ion Concentration
Sulfide:quinone oxidoreductase (SQOR) is a membrane-bound enzyme that catalyzes the first step in the mitochondrial metabolism of H(2)S. Human SQOR is successfully expressed at low temperature in Escherichia coli by using an optimized synthetic gene and cold-adapted chaperonins. Recombinant SQOR contains noncovalently bound FAD and catalyzes the two-electron oxidation of H(2)S to S(0) (sulfane sulfur) using CoQ(1) as an electron acceptor. The prosthetic group is reduced upon anaerobic addition of H(2)S in a reaction that proceeds via a long-wavelength-absorbing intermediate (λ(max) = 673 nm). Cyanide, sulfite, or sulfide can act as the sulfane sulfur acceptor in reactions that (i) exhibit pH optima at 8.5, 7.5, or 7.0, respectively, and (ii) produce thiocyanate, thiosulfate, or a putative sulfur analogue of hydrogen peroxide (H(2)S(2)), respectively. Importantly, thiosulfate is a known intermediate in the oxidation of H(2)S by intact animals and the major product formed in glutathione-depleted cells or mitochondria. Oxidation of H(2)S by SQOR with sulfite as the sulfane sulfur acceptor is rapid and highly efficient at physiological pH (k(cat)/K(m,H(2)S) = 2.9 × 10(7) M(-1) s(-1)). A similar efficiency is observed with cyanide, a clearly artificial acceptor, at pH 8.5, whereas a 100-fold lower value is seen with sulfide as the acceptor at pH 7.0. The latter reaction is unlikely to occur in healthy individuals but may become significant under certain pathological conditions. We propose that sulfite is the physiological acceptor of the sulfane sulfur and that the SQOR reaction is the predominant source of the thiosulfate produced during H(2)S oxidation by mammalian tissues.

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Web of Science research areas
Biochemistry & Molecular Biology
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