A putative multicopper oxidase, IoxA, is involved in iodide oxidation by Roseovarius sp strain A-2

作者：Shiroyama Kanna; Kawasaki Yasutaka; Unno Yusuke; Amachi Seigo^*

来源：Bioscience Biotechnology and Biochemistry, 2015, 79(11): 1898-1905.

DOI：10.1080/09168451.2015.1052767

• iodide oxidation
• multicopper oxidase
• IoxA
• Roseovarius

Roseovarius sp. strain A-2 is an aerobic heterotrophic bacterium with a capacity for oxidizing iodide ion (I-) to form molecular iodine (I-2). In this study, iodide-oxidizing enzyme of strain A-2 was characterized. The enzyme was an extracellular protein, and Cu2+ ion significantly enhanced the enzyme activity in the culture supernatant. When iodide was used as the substrate, the crude enzyme showed Km and V-max 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.

• 出版日期2015