Structure and Electron Transfer of Quinoproteins and application to Bio-electrode Devices

1)组胺脱氢酶的结构分析和电子转移特性研究表明，组胺脱氢酶含有6-S-胞嘧啶-FMN和4Fe-4S簇作为氧化还原辅基。在中性条件下，底物对每个单体进行2电子还原，而在pH 9.5以上，电子数切换到单位。这些性质可以用氧化还原电势的变化来解释。用停流法分析了半还原反应的动力学。HmDH的全息形式已在大肠杆菌中表达，其纯度为100%。定点突变提高了酶的专一性。2)藜麦血球蛋白的电子转移在蛋白脱氢酶活性中心附近的正电荷对电子受体的电子转移起着重要的作用。未观察到QH-AMDH向电极的直接电子转移。藜麦血红蛋白乙醇脱氢酶的氧化还原电位与pH有关。这可能是由于酶的结构发生了变化。3)在生物传感器和生物燃料电池中的应用研究发现，突变体HmDH对组胺具有很好的催化作用，具有很高的特异性。中间体的选择性降低了干扰。以胆红素氧化酶(BOD)为阴极酶，将所合成的脱氢酶应用于生物燃料电池的生物阳极。BOD的直接电子转移受电极材料的影响。电流密度提高了几十mA cm~(-2)。

1)Structural analysis and Electron Transfer Characteristics of Histamine Dehydrogenase (HmDH)It has been revealed that HmDH has 6-S-cyteinyl-FMN and 4Fe-4S cluster as redox prosthetic groups. Under neutral conditions, 2-electron reductions occurs per monomer by the substrate, while the number of the electron is switched to unit over pH 9.5. The properties can be explained in terms of the change in the redox potentials. The kinetics of half-reduction has been analyzed with stopped flow method. The holo form of HmDH has been expressed in E.coli in the purity of 100%. Site-directed mutation improve the specificity of the enzyme.2)Electron Transfer of QuinohemoproteinsPositive charge in the vicinity of the active site of quinohemoprotein amine dehydrogenase (QH-AmDH) plays an important role in the electron transfer from to electron acceptor. The direct electron transfer from QH-AmDH to electrodes was not observed. The redox potentials of quinohemoproteins alcohol dehydrogenase depend on pH. This would be due to the structural change of the enzyme.3)Application to Biosensor and Biofuel CellsIt has been found that mutant HmDH works as a good catalysis of mediated biosensor for histamine with high specificity. Selectivity of mediator reduced the interference. The dehydrogenases invested here were utilized also as catalysts in bioanode of biofuel cells, where bilirubin oxidase (BOD) was used as cathode enzyme. Direct electron transfer of BOD is affected by the electrode materials. The current density were increased up few ten mA cm^<-2>.