Department of Physical Chemistry, Babeş-Bolyai University, Arany Janos 11, 400028 Cluj-Napoca, Romania.
Bioelectrochemistry. 2012 Dec;88:84-91. doi: 10.1016/j.bioelechem.2012.06.006. Epub 2012 Jun 29.
The electrochemical characterization of a class II cellobiose dehydrogenase (CDH), from the ascomycete fungus Neurospora crassa, adsorbed on graphite (G), was performed in regard to direct (DET) and mediated electron transfer (MET). The effects of the applied potential, mediator (1,4 benzoquinone) concentration and flow carrier pH on the amperometric response of the G/CDH modified electrodes were investigated under flow conditions. From the calibration curves, recorded at two pH values (5.2 and 7.0) for nine different sugars, the kinetic and the analytical parameters were evaluated under DET and MET operation modes. These results together with those obtained from long term operational stability measurements showed that: (i) for all nine investigated sugars the sensitivity was higher for MET than for DET and for pH 5.2 compared to pH 7.0; (ii) irrespective of DET or MET operation mode, the sensitivity of the new enzyme towards the investigated sugars decreased in the following sequence: cellobiose>lactose>(cellotriose≈cellopentaose) >>(maltotriose≈maltotetraose≈maltopentaose)>(maltose≈glucose); (iii) for all tested substrates, the apparent CDH affinity was roughly higher in DET than in MET operation mode.
对一种 II 类纤维二糖脱氢酶（CDH）（来自曲霉菌 Neurospora crassa）在石墨（G）上的电化学特性进行了研究，涉及直接（DET）和介导电子转移（MET）。在流动条件下，研究了施加电位、介体（1,4-苯醌）浓度和流动载体 pH 对 G/CDH 修饰电极的电流响应的影响。根据在两个 pH 值（5.2 和 7.0）下记录的九条不同糖的校准曲线，在 DET 和 MET 操作模式下评估了动力学和分析参数。这些结果以及从长期操作稳定性测量中获得的结果表明：（i）对于所有九种研究的糖，MET 比 DET 的灵敏度更高，在 pH 5.2 比 pH 7.0 更高；（ii）无论 DET 还是 MET 操作模式，新酶对研究的糖的灵敏度按以下顺序降低：纤维二糖>乳糖>（纤维三糖≈纤维五糖）>（麦芽三糖≈麦芽四糖≈麦芽五糖）>（麦芽糖≈葡萄糖）；（iii）对于所有测试的底物，在 DET 操作模式下，CDH 的表观亲和力大致高于 MET 操作模式。
