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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >Mechanism of versatile peroxidase inactivation by Ca2+ depletion
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Mechanism of versatile peroxidase inactivation by Ca2+ depletion

机译：Ca2 +耗竭导致多种过氧化物酶失活的机理

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摘要

Versatile peroxidase (VP) from Bjerkandera adusta, as other class II peroxidases, is inactivated by Ca2+ depletion. In this work, the spectroscopic characterizations of Ca2+-depleted VP at pH 4.5 (optimum for activity) and pH 7.5 are presented. Previous works on other ligninolytic peroxidases, such as lignin peroxidase and manganese peroxidase, have been performed at pH 7.5; nevertheless, at this pH these enzymes are inactive independently of their Ca2+ content. At pH 7.5, UV-Vis spectra indicate a heme-Fe3+ transition from 5-coordinated high-spin configuration in native peroxidase to 6-coordinated low-spin state in the inactive Ca2+-depleted form. This Fe3+ hexa-coordination has been proposed as the origin of inactivation. However, our results at pH 4.5 show that Ca2+-depleted enzyme has a high spin Fe3+. EPR measurements on VP confirm the differences in the Fe3+ spin states at pH 4.5 and at 7.5 for both, native and Ca2+-depleted enzymes. In addition, EPR spectra recorded after the addition of H2O2 to Ca2+-depleted VP show the formation of compound I with the radical species delocalized on the porphyrin ring. The lack of radical delocalization on an amino acid residue exposed to solvent, W170, as determined in native enzyme at pH 4.5, explains the inability of Ca2+-depleted VP to oxidize veratryl alcohol. These observations, in addition to a notorious redox potential decrease, suggest that Ca2+-depleted versatile peroxidase is able to form the active intermediate compound I but its long range electron transfer has been disrupted. (c) 2006 Elsevier B.V. All rights reserved.
机译：与其他II类过氧化物酶一样，来自Bjerkandera adusta的通用过氧化物酶（VP）通过Ca2 +消耗而失活。在这项工作中，提出了在pH 4.5（活性最佳）和pH 7.5时Ca2 +耗尽的VP的光谱表征。先前对其他木质素过氧化物酶的研究（例如木质素过氧化物酶和锰过氧化物酶）已在pH 7.5下进行;但是，在此pH值下，这些酶无活性，而与其Ca2 +含量无关。在pH 7.5时，UV-Vis光谱表明血红素-Fe3 +从天然过氧化物酶中的5配位的高自旋构型转变为无活性的Ca2 +耗尽形式的6配位的低旋态。已经提出该Fe 3+六配位作为失活的起源。但是，我们在pH 4.5时的结果表明，贫Ca2 +的酶具有较高的自旋Fe3 +。 VP上的EPR测量证实了天然和贫Ca2 +酶在pH 4.5和7.5时Fe3 +自旋态的差异。此外，在向贫Ca2 +的VP中添加H2O2后记录的EPR光谱显示，形成的化合物I的自由基种类在卟啉环上是非局部的。在pH 4.5的天然酶中测定，暴露于溶剂W170的氨基酸残基上没有自由基离域，这说明缺乏Ca2 +的VP无法氧化藜芦醇。这些发现，除了臭名昭著的氧化还原电势下降外，还表明，贫化了Ca2 +的通用过氧化物酶能够形成活性中间体化合物I，但其远距离电子转移受到干扰。 （c）2006 Elsevier B.V.保留所有权利。

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