School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, 4072, Australia.
Center for Integrated Protein Science Munich (CIPSM) and Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, Haus D, 81377, München, Germany.
Chemistry. 2019 Jul 2;25(37):8760-8768. doi: 10.1002/chem.201900525. Epub 2019 May 20.
We report the first electrochemical study of a lanthanoid-dependent methanol dehydrogenase (Eu-MDH) from the acidophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV with its own physiological cytochrome c electron acceptor. Eu-MDH harbours a redox active 2,7,9-tricarboxypyrroloquinoline quinone (PQQ) cofactor which is non-covalently bound but coordinates trivalent lanthanoid elements including Eu . Eu-MDH and the cytochrome were co-adsorbed with the biopolymer chitosan and cast onto a mercaptoundecanol (MU) monolayer modified Au working electrode. Cyclic voltammetry of cytochrome c reveals a well-defined quasi-reversible Fe redox couple at +255 mV vs. NHE at pH 7.5 and this response is pH independent. The reversible one-electron response of the cytochrome c transforms into a sigmoidal catalytic wave in the presence of Eu-MDH and its substrates (methanol or formaldehyde). The catalytic current was pH-dependent and pH 7.3 was found to be optimal. Kinetic parameters (pH dependence, activation energy) obtained by electrochemistry show the same trends as those obtained from an artificial phenazine ethosulfate/dichlorophenol indophenol assay.
我们报告了首例电化学研究，研究对象为嗜酸疣微菌甲烷营养菌甲基嗜酸菌中依赖镧系元素的甲醇脱氢酶（Eu-MDH），该酶有其自身的生理细胞色素 c 电子受体。Eu-MDH 含有氧化还原活性的 2,7,9-三羧酸吡咯并喹啉醌（PQQ）辅因子，该辅因子通过非共价键结合，但与包括 Eu 在内的三价镧系元素配位。Eu-MDH 和细胞色素被与壳聚糖生物聚合物共同吸附，并涂覆到巯基十一烷醇（MU）单层修饰的 Au 工作电极上。细胞色素 c 的循环伏安法在 pH 7.5 时，于+255 mV 对 NHE 处显示出定义明确的准可逆 Fe 氧化还原对，且该响应与 pH 无关。在存在 Eu-MDH 和其底物（甲醇或甲醛）的情况下，细胞色素 c 的可逆单电子响应转变为类正弦催化波。催化电流与 pH 有关，pH 7.3 被发现是最佳的。通过电化学获得的动力学参数（pH 依赖性、活化能）与通过人工吩嗪乙硫醚/二氯酚靛酚测定法获得的动力学参数具有相同的趋势。
