Direct electron transfer from graphite and functionalized gold electrodes to T1 and T2/T3 copper centers of bilirubin oxidase
Direct electron transfer from graphite and functionalized gold electrodes to T1 and T2/T3 copper centers of bilirubin oxidase
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DOI：
10.1016/j.bbabio.2008.06.010
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发表时间：
2008-10-01
影响因子：
4.3
通讯作者：
Shleev, Sergey
中科院分区：
文献类型：
--
作者：
Ramirez, Pablo;Mano, Nicolas;Shleev, Sergey
采用循环伏安法和时间电流法研究了裸石墨（SPGE）和3-巯基丙酸修饰金（MPA-gold）电极向太阳厚皮胆红素氧化酶（BOD）的直接电子转移（DET）。在循环伏安图上，可以清楚地观察到与酶T1位点和T2/T3簇的氧化还原转化相对应的中点电位约为700 mV和400 mV的非周转法拉第信号。固定化BOD在两个电极上的取向不同，其对o -2电还原的催化作用也有很大差异。在SPGE上，大部分酶被靠近碳的T1铜位点定向，ET过程相当缓慢，观察到O-2的明显的det -生物电还原，与NHE相比，从bb0 700 mV开始。相反，在MPA-gold上，大部分酶的T2/T3铜簇靠近金属取向。事实上，尽管MPA-gold和BOD的T2/T3铜簇之间的ET与SPGE在T1位点观察到的ET相似，但几乎没有基于det的o -2电还原催化。当BOD活性催化o -2电还原时，其T1位点相对于NHE的氧化还原电位为690 mV，其中一个T2/T3铜中心相对于NHE的氧化还原电位为390 mV。与NHE相比，静息态BOD的T2/T3铜簇的氧化还原电位约为360 mV。结合观察到的生物催化行为，这些值强烈表明，在酶的催化转换过程中，分子内电子从T1位点向上转移到T2/T3簇。(C) 2008 Elsevier B.V.版权所有
Direct electron transfer (DET) from bare spectrographic graphite (SPGE) or 3-mercaptopropionic acid-modified gold (MPA-gold) electrodes to Trachyderma tsunodae bilirubin oxidase (BOD) was studied under anaerobic and aerobic conditions by cyclic voltammetry and chronoamperometry. On cyclic voltammograms nonturnover Faradaic signals with midpoint potentials of about 700 mV and 400 mV were clearly observed corresponding to redox transformations of the T1 site and the T2/T3 cluster of the enzyme, respectively. The immobilized BOD was differently oriented on the two electrodes and its catalysis of O-2-electroreduction was also massively different. On SPGE, where most of the enzyme was oriented with the T1 copper site proximal to the carbon with a quite slow ET process, well-pronounced DET-bioelectroreduction of O-2 was observed, starting already at > 700 mV vs. NHE. In contrast, on MPA-gold most of the enzyme was oriented with its T2/T3 copper cluster proximal to the metal. Indeed, there was little DET-based catalysis of O-2-electroreduction, even though the ET between the MPA-gold and the T2/T3 copper cluster of BOD was similar to that observed for the T1 site at SPGE. When BOD actively catalyzes the O-2-electroreduction, the redox potential of its T1 site is 690 mV vs. NHE and that of one of its T2/T3 copper centers is 390 mV vs. NHE. The redox potential of the T2/T3 copper cluster of a resting form of BOD is suggested to be about 360 mV vs. NHE. These values, combined with the observed biocatalytic behavior, strongly suggest an uphill intra-molecular electron transfer from the T1 site to the T2/T3 cluster during the catalytic turnover of the enzyme. (C) 2008 Elsevier B.V. All rights reserved.