Journal
ARCHIVES OF MICROBIOLOGY
Volume 189, Issue 1, Pages 59-69Publisher
SPRINGER
DOI: 10.1007/s00203-007-0293-y
Keywords
manganese oxidation; PQQ; erythrobacter; multicopper oxidase
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Funding
- NATIONAL INSTITUTE OF ENVIRONMENTAL HEALTH SCIENCES [P42ES010337] Funding Source: NIH RePORTER
- NIEHS NIH HHS [P42 ES010337-050009, ES10337, P42 ES010337-070009, P42 ES010337-060009, P42 ES010337-040009, P42 ES010337] Funding Source: Medline
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Manganese(II)-oxidizing bacteria play an integral role in the cycling of Mn as well as other metals and organics. Prior work with Mn(II)-oxidizing bacteria suggested that Mn(II) oxidation involves a multicopper oxidase, but whether this enzyme directly catalyzes Mn(II) oxidation is unknown. For a clearer understanding of Mn(II) oxidation, we have undertaken biochemical studies in the model marine alpha-proteobacterium, Erythrobacter sp. strain SD21. The optimum pH for Mn(II)-oxidizing activity was 8.0 with a specific activity of 2.5 nmol x min(-1) x mg(-1) and a K-m = 204 mu M. The activity was soluble suggesting a cytoplasmic or periplasmic protein. Mn(III) was an intermediate in the oxidation of Mn(II) 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 Mn(II)-oxidizing mutants with insertions in the anthranilate synthase gene. The substrate and product of anthranilate synthase are intermediates in various quinone biosyntheses. Partially purified Mn(II) 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 Mn(II) oxidation.
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