Department of Chemistry, University of Florida, P.O. Box 117200, Gainesville, FL 32611-7200, USA.
Arch Biochem Biophys. 2011 May 1;509(1):100-7. doi: 10.1016/j.abb.2011.02.022. Epub 2011 Mar 2.
Oxalate oxidase (E.C. 1.2.3.4) catalyzes the oxygen-dependent oxidation of oxalate to carbon dioxide in a reaction that is coupled with the formation of hydrogen peroxide. Although there is currently no structural information available for oxalate oxidase from Ceriporiopsis subvermispora (CsOxOx), sequence data and homology modeling indicate that it is the first manganese-containing bicupin enzyme identified that catalyzes this reaction. Interestingly, CsOxOx shares greatest sequence homology with bicupin microbial oxalate decarboxylases (OxDC). We show that CsOxOx activity directly correlates with Mn content and other metals do not appear to be able to support catalysis. EPR spectra indicate that the Mn is present as Mn(II), and are consistent with the coordination environment expected from homology modeling with known X-ray crystal structures of OxDC from Bacillus subtilis. EPR spin-trapping experiments support the existence of an oxalate-derived radical species formed during turnover. Acetate and a number of other small molecule carboxylic acids are competitive inhibitors for oxalate in the CsOxOx catalyzed reaction. The pH dependence of this reaction suggests that the dominant contribution to catalysis comes from the monoprotonated form of oxalate binding to a form of the enzyme in which an active site carboxylic acid residue must be unprotonated.
草酸氧化酶（EC 1.2.3.4）在与过氧化氢形成偶联的反应中，催化草酸盐在氧气存在下氧化为二氧化碳。虽然目前Ceriporiopsis subvermispora（CsOxOx）的草酸氧化酶尚无结构信息，但序列数据和同源建模表明，它是第一个鉴定出的含有锰的双cupin 酶，催化此反应。有趣的是，CsOxOx 与双 cupin 微生物草酸脱羧酶（OxDC）具有最大的序列同源性。我们表明，CsOxOx 的活性与 Mn 含量直接相关，其他金属似乎无法支持催化。EPR 谱表明 Mn 以 Mn(II)的形式存在，与已知枯草芽孢杆菌 OxDC 的 X 射线晶体结构的同源建模所预期的配位环境一致。EPR 自旋捕获实验支持在周转过程中形成草酸盐衍生的自由基物种。乙酸盐和许多其他小分子羧酸是 CsOxOx 催化反应中草酸盐的竞争性抑制剂。该反应的 pH 依赖性表明，催化作用的主要贡献来自于单质子化形式的草酸盐与酶的一种形式结合，其中必须使活性位点的羧酸残基去质子化。
