Authors: Hope A Johnson Bradley M Tebo
Publish Date: 2007/08/03
Volume: 189, Issue: 1, Pages: 59-69
Abstract
ManganeseIIoxidizing bacteria play an integral role in the cycling of Mn as well as other metals and organics Prior work with MnIIoxidizing bacteria suggested that MnII oxidation involves a multicopper oxidase but whether this enzyme directly catalyzes MnII oxidation is unknown For a clearer understanding of MnII oxidation we have undertaken biochemical studies in the model marine αproteobacterium Erythrobacter sp strain SD21 The optimum pH for MnIIoxidizing activity was 80 with a specific activity of 25 nmol × min−1 × mg−1 and a K m = 204 μM The activity was soluble suggesting a cytoplasmic or periplasmic protein MnIII was an intermediate in the oxidation of MnII and likely the primary product of enzymatic oxidation The activity was stimulated by pyrroloquinoline quinone PQQ NAD+ and calcium but not by copper In addition PQQ rescued Pseudomonas putida MnB1 non MnIIoxidizing mutants with insertions in the anthranilate synthase gene The substrate and product of anthranilate synthase are intermediates in various quinone biosyntheses Partially purified MnII oxidase was enriched in quinones and had a UV/VIS absorption spectrum similar to a known quinone requiring enzyme but not to multicopper oxidases These studies suggest that quinones may play an integral role in bacterial MnII oxidationWe thank Cassandra Gaston Patrizia Pretto James McCarthy and Greg Dick for laboratory assistance and helpful discussions We thank Hans Duine for generously supplying soluble glucose dehydrogenase apoenzyme We thank the Gordon and Betty Moore Foundation and The Venter Institute for Genome Sequencing of Erythrobacter sp SD21 This research was funded by grants from the National Science Foundation CHE0089208 and MCB0630355 and a Superfund Basic Research Program Grant to UCSD NIEHS ES10337
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