title: Molecular characterization of the membrane-bound quinol peroxidase functionally connected to the respiratory chain.
abstract: Here, we report for the first time quinol peroxidase (QPO), an enzyme that uses ubiquinol-1 as an electron donor for the reduction of H(2)O(2) to water. We purified QPO to > 90% purity from the membrane fraction of Actinobacillus actinomycetemcomitans. QPO is a 53.6-kDa protein that contains three heme c molecules. The qpo gene was predicted to encode a putative bacterial cytochrome c peroxidase with N-terminal extensions containing an additional potential heme c-binding motif. Although qpo has high sequence homology to bacterial cytochrome c peroxidases, QPO did not catalyze peroxidation in the presence of horse heart cytochrome c. In addition, the cytoplasmic membrane of A. actinomycetemcomitans had apparent QPO-dependent peroxidase activity in the presence of NADH or succinate, which are substrates for the respiratory chain. Based on these findings, we present a new mechanism for the scavenging of reactive oxygen species in which quinol in the respiratory chain is consumed.
authors.affiliation: Department of Microbiology, School of Life Dentistry at Tokyo, Nippon Dental University, Tokyo, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamada
authors.forename: Eizo
authors.initials: E
authors.lastname: Takashima
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Konishi
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D016227:Benzoquinones / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D004579:Electron Transport; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein; D013053:Spectrophotometry; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D016227:Benzoquinones; D009243:NAD; C004532:quinone; D019802:Succinic Acid; D010544:Peroxidases; D002118:Calcium