title: Enzymatic characterization and in vivo function of five terminal oxidases in Pseudomonas aeruginosa.
abstract: The ubiquitous opportunistic pathogen Pseudomonas aeruginosa has five aerobic terminal oxidases: bo(3)-type quinol oxidase (Cyo), cyanide-insensitive oxidase (CIO), aa3-type cytochrome c oxidase (aa3), and two cbb(3)-type cytochrome c oxidases (cbb(3)-1and cbb(3)-2). These terminal oxidases are differentially regulated under various growth conditions and are thought to contribute to the survival of this microorganism in a wide variety of environmental niches. Here, we constructed multiple mutant strains of P. aeruginosa that express only one aerobic terminal oxidase to investigate the enzymatic characteristics and in vivo function of each enzyme. The Km values of Cyo, CIO, and aa3 for oxygen were similar and were 1 order of magnitude higher than those of cbb(3)-1 and cbb(3)-2, indicating that Cyo, CIO, and aa3 are low-affinity enzymes and that cbb(3)-1 and cbb(3)-2 are high-affinity enzymes. Although cbb(3)-1 and cbb(3)-2 exhibited different expression patterns in response to oxygen concentration, they had similar Km values for oxygen. Both cbb(3)-1 and cbb(3)-2 utilized cytochrome c4 as the main electron donor under normal growth conditions. The electron transport chains terminated by cbb(3)-1 and cbb(3)-2 generate a proton gradient across the cell membrane with similar efficiencies. The electron transport chain of aa3 had the highest proton translocation efficiency, whereas that of CIO had the lowest efficiency. The enzymatic properties of the terminal oxidases reported here are partially in agreement with their regulatory patterns and may explain the environmental adaptability and versatility of P. aeruginosa.
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan aharai@mail.ecc.u-tokyo.ac.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Arai
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Takuro
authors.initials: T
authors.lastname: Kawakami
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Osamura
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Hirai
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Sakai
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ishii
mesh_terms: D004579:Electron Transport; D020869:Gene Expression Profiling; D055786:Gene Knockout Techniques; D007700:Kinetics; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000201:enzymology* / Q000235:genetics
chemical_list: D010088:Oxidoreductases; D010100:Oxygen