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首页> 外文期刊>Biochemistry >Kinetics and Reactivity of the Flavin and Heme Cofactors of Cellobiose Dehydrogenase from Phanerochaete chrysosporium
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Kinetics and Reactivity of the Flavin and Heme Cofactors of Cellobiose Dehydrogenase from Phanerochaete chrysosporium

机译：Phanerochaete chrysosporium纤维二糖脱氢酶的黄素和血红素辅因子的动力学和反应性

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The flavin cofactor within cellobiose dehydrogenase (CDH) was found to be responsible for the reduction of all electron acceptors tested.This includes cytochrome c,the reduction of which has been reported to be by the reduced heme of CDH.The heme group was shown to affect the reactivity and activation energy with respect to individual electron acceptors,but the heme group was not involved in the direct transfer of electrons to substrate.A complicated interaction was found to exist between the flavin and heme of cellobiose dehydrogenase. The addition of electron acceptors was shown to increase the rate of flavin reduction and the electron transfer rate between the flavin and heme.All electron acceptors tested appeared to be reduced by the flavin domain.The addition of ferric iron eliminated the flavin radical present in reduced CDH,as detected by low temperature ESR spectroscopy,while it increased the flavin redical ESR signal in the independent flavin domain,more commonly referred to as cellobiose: quinone oxidoreductase (CBQR).Conversely,no radical was detected with either CDH or CBQR upon the addition of methyl-1,4--benazoquinone.Similar reaction rates and activation energies were determined for methyl-1,4-benzoquinone with both CDH and CBQR,whereas the rate of iron reduction by CDH was five times higher than by CBQR,and its activation energy was 38 kJ/mol lower than that of CBQR.Oxygen,which may be reduced by either one or two electrons,was found to behave like a two-electron acceptor.Superoxide production was found only upon the inclusion of iron.Additionally,information is presented indicating that the site of substrate reduction may be in the cleft between the flavin and heme domains.
机译：发现纤维二糖脱氢酶（CDH）中的黄素辅因子可减少所有测试的电子受体，其中包括细胞色素c，据报道其减少是由于CDH血红素减少所致。影响血红素基团与单电子受体的反应性和活化能，但血红素基团不参与电子直接转移至底物。纤维二糖脱氢酶的黄素和血红素之间存在复杂的相互作用。研究表明，加入电子受体可以提高黄素的还原率以及黄素和血红素之间的电子转移速率。所有测试的电子受体似乎都被黄素域还原了。三价铁的加入消除了还原中存在的黄素自由基CDH，通过低温ESR光谱检测，同时增加了独立的黄素结构域中的黄素ESR信号，通常称为纤维二糖：醌氧化还原酶（CBQR）。相反，在CDH或CBQR时未检测到自由基测定了CDH和CBQR的1,4-甲基苯醌的相似反应速率和活化能，而CDH的铁还原速率是CBQR的五倍，并且它的活化能比CBQR低38 kJ / mol。发现可能被一个或两个电子还原的氧表现得像一个二电子受体。 d。仅显示出铁的信息。另外，信息表明底物还原的位点可能在黄素和血红素结构域之间的缝隙中。

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