title: Menaquinone reduction by an HMT2-like sulfide dehydrogenase from Bacillus stearothermophilus.
abstract: The gene-encoding HMT2-like sulfide dehydrogenase from Bacillus stearothermophilus JCM2501 was amplified and expressed in Escherichia coli and the enzymatic features were examined. The enzyme was detected mainly in the membrane fraction. It catalyzed the sulfide-dependent menaquinone (MK) reduction showing special enzymatic features distinct from other sulfide-quinone oxidoreductases (SQRs) from autotrophic bacteria. The purified protein from E. coli brought about the sulfide-dependent 2,3-dimethyl-1,4-naphthoquinone (DMN) reduction in vitro. The reduction was accelerated in the presence of either cyanide or 2-mercaptoethanol and phospholipids. The high reduction was followed by a change in Km values for sulfide and DMN. The purified enzyme utilized MK as an electron acceptor in the membrane fraction from E. coli. Under anaerobic conditions, sulfide was oxidized with reduction of fumarate or nitrate via the MK pool. The dehydrogenase was different from SQR in autotrophic bacteria in terms of the low affinity for sulfide and the activity enhancement in the presence of cyanide or 2-mercaptoethanol. The sulfide oxidation via MK in the cellular membrane of Gram-positive bacteria was certified.
authors.affiliation: School of Agriculture, Meiji University, Higashimita 1-1-1, Tama-ku, Kawasaki, 214-8571 Japan.
authors.forename: Hiroomi
authors.initials: H
authors.lastname: Shibata
authors.forename: Kuniyuki
authors.initials: K
authors.lastname: Suzuki
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D000595:Amino Acid Sequence; D000693:Anaerobiosis; D002462:Cell Membrane / Q000201:enzymology; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005650:Fumarates / Q000378:metabolism; D001411:Geobacillus stearothermophilus / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D006358:Hot Temperature; D007700:Kinetics; D008969:Molecular Sequence Data; D009566:Nitrates; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D013440:Sulfides / Q000378:metabolism*; D024482:Vitamin K 2 / Q000378:metabolism*
chemical_list: D005650:Fumarates; D009566:Nitrates; D013440:Sulfides; D024482:Vitamin K 2; D010088:Oxidoreductases