In vitro studies indicate a quinone is involved in bacterial Mn(II) oxidation
In vitro studies indicate a quinone is involved in bacterial Mn(II) oxidation
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DOI：
10.1007/s00203-007-0293-y
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发表时间：
2008-01-01
影响因子：
2.8
通讯作者：
Tebo, Bradley M.
中科院分区：
文献类型：
--
作者：
Johnson, Hope A.;Tebo, Bradley M.
锰(II)氧化细菌在锰以及其他金属和有机物的循环中起着不可或缺的作用。以前对锰(II)氧化细菌的研究表明，锰(II)氧化涉及一个多铜氧化酶，但该酶是否直接催化锰(II)氧化尚不清楚。为了更清楚地了解Mn(II)的氧化，我们对海洋α-变形杆菌进行了生化研究。菌株SD21。其最适pH为8.0，比活力为2.5nmolxmin(-1)×mg(-1)，K-m=204mM，活性为可溶性，提示为细胞质或周质蛋白。Mn(III)是Mn(II)氧化的中间产物，很可能是酶催化氧化的初级产物。吡咯喹啉醌(PQQ)、NAD(+)和钙对酶活性有明显的刺激作用，而铜对酶活性无明显影响。此外，PQQ还通过插入邻氨基苯甲酸合成酶基因拯救了恶臭假单胞菌MnB1非Mn(II)氧化突变体。邻氨基苯甲酸合成酶的底物和产物是各种苯醌生物合成的中间产物。部分纯化的Mn(II)氧化酶富含苯二酚，其紫外/可见吸收光谱与已知的需要酶的苯醌相似，但与多铜氧化酶不同。这些研究表明，苯二酚可能在细菌的锰(II)氧化中起着不可或缺的作用。
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.