title: A putative multicopper oxidase, IoxA, is involved in iodide oxidation by Roseovarius sp. strain A-2.
abstract: Roseovarius sp. strain A-2 is an aerobic heterotrophic bacterium with a capacity for oxidizing iodide ion (I(-)) to form molecular iodine (I2). In this study, iodide-oxidizing enzyme of strain A-2 was characterized. The enzyme was an extracellular protein, and Cu(2+) ion significantly enhanced the enzyme activity in the culture supernatant. When iodide was used as the substrate, the crude enzyme showed Km and Vmax values of 4.78 mM and 25.1 U mg(-1), respectively. The enzyme was inhibited by NaN3, EDTA, KCN, and o-phenanthroline, and also had significant activities toward p-phenylenediamine and hydroquinone. Tandem mass spectrometric analysis of an active band excised from SDS-PAGE gel revealed that at least two proteins are involved in the enzyme. One of these proteins was closely related with IoxA, a multicopper oxidase previously found as a component of iodide-oxidizing enzyme of Alphaproteobacterium strain Q-1. Furthermore, a terrestrial bacterium Rhodanobacter denitrificans 116-2, which possesses an ioxA-like gene in its genome, was found to oxidize iodide. These results suggest that IoxA catalyzes the oxidation of iodide in phylogenetically distinct bacteria.
authors.affiliation: a Graduate School of Horticulture , Chiba University , Matsudo-city , Japan.
authors.forename: Kanna
authors.initials: K
authors.lastname: Shiroyama
authors.affiliation: a Graduate School of Horticulture , Chiba University , Matsudo-city , Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Kawasaki
authors.affiliation: b Institute for Environmental Sciences , Kamikita-gun , Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Unno
authors.affiliation: a Graduate School of Horticulture , Chiba University , Matsudo-city , Japan.
authors.forename: Seigo
authors.initials: S
authors.lastname: Amachi
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D003300:Copper / Q000737:chemistry / Q000378:metabolism; D007454:Iodides / Q000737:chemistry / Q000378:metabolism*; D007477:Ions / Q000737:chemistry; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D041902:Rhodobacteraceae / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D007454:Iodides; D007477:Ions; D012336:RNA, Ribosomal, 16S; D003300:Copper; D010088:Oxidoreductases
keywords: IoxA; Roseovarius; iodide oxidation; multicopper oxidase