title: Specificity of respiratory pathways involved in the reduction of sulfur compounds by Salmonella enterica.
abstract: The tetrathionate (Ttr) and thiosulfate (Phs) reductases of Salmonella enterica LT2, together with the polysulfide reductase (Psr) of Wolinella succinogenes, are unusual examples of enzymes containing a molybdopterin active-site cofactor since all formally catalyse sulfur-sulfur bond cleavage. This is in contrast to the oxygen or hydrogen transfer reactions exhibited by other molybdopterin enzymes. Here the catalytic specificity of Ttr and Phs has been compared using both physiological and synthetic electron-donor systems. Ttr is shown to catalyse reduction of trithionate but not sulfur or thiosulfate. In contrast, Phs cannot reduce tetrathionate or trithionate but allows whole cells to utilize elemental sulfur as an electron acceptor. Mechanisms are proposed by which the bacterium is able to utilize an insoluble sulfur substrate by means of reactions at the cytoplasmic rather than the outer membrane.
authors.affiliation: Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Hinsley
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK2.|Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK1.
authors.forename: Ben C
authors.initials: BC
authors.lastname: Berks
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002384:Catalysis; D003545:Cysteine / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D050862:Oxidoreductases Acting on Sulfur Group Donors; D012119:Respiration; D019779:Salmonella enterica / Q000201:enzymology / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013455:Sulfur / Q000378:metabolism; D013456:Sulfur Acids / Q000378:metabolism; D013457:Sulfur Compounds / Q000378:metabolism*; D013466:Sulfurtransferases
chemical_list: D013456:Sulfur Acids; D013457:Sulfur Compounds; C009597:trithionic acid; D013455:Sulfur; D010088:Oxidoreductases; C022727:tetrathionate reductase; D050862:Oxidoreductases Acting on Sulfur Group Donors; C074883:polysulfide reductase; D013466:Sulfurtransferases; C022747:thiosulfate-dithiol sulfurtransferase; D003545:Cysteine