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

1)组胺脱氢酶（HmDH）的结构分析和电子转移特性研究表明，HmDH含有6-S-半胱氨酰-FMN和4Fe-4S簇作为氧化还原辅基。在中性条件下，每个单体通过底物发生2-电子还原，而电子数在pH 9.5以上切换为单位。这些性质可以用氧化还原电位的变化来解释。用停流法分析了半还原动力学。在大肠杆菌中表达了HmDH的完整形式，纯度为100%。定点突变提高了酶的专一性。2）喹诺血红素蛋白的电子转移喹诺血红素蛋白胺脱氢酶（QH-AmDH）活性中心附近的正电荷在电子从受体到受体的转移中起着重要作用。没有观察到从QH-AmDH到电极的直接电子转移。醌血红素蛋白醇脱氢酶的氧化还原电位依赖于pH值，这可能是由于酶的结构发生了变化。3）生物传感器和生物燃料电池的应用研究发现，突变型HmDH作为介导型组胺生物传感器的催化剂，具有很好的特异性。介质的选择性降低了干扰。在生物燃料电池的生物阳极中，胆红素氧化酶（BOD）被用作阴极酶。电极材料对BOD的直接电子转移有影响。电流密度增加了几十mA cm ↑ [2]<-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>.