马肝醇脱氢酶中蓝色铜中心的电子顺磁共振研究。

An EPR study of the blue copper center in horse liver alcohol dehydrogenase.

作者信息

Maret W, Zeppezauer M, Desideri A, Morpurgo L, Rotilio G

出版信息

Biochim Biophys Acta. 1983 Mar 16;743(2):200-6. doi: 10.1016/0167-4838(83)90214-5.

Abstract

Active-site specifically reconstituted Cu2+ horse liver alcohol dehydrogenase (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) shows optical and EPR spectra similar to those of native blue copper (Type 1) proteins. EPR spectra at different temperatures and frequencies reveal a heterogeneity of the copper center: a minor 'non-blue' species with axial line shape (g parallel = 2.16, g perpendicular = 2.04; A parallel = 100 x 10(-4) cm-1), which accounts for approximately 10% of the total copper and is not accessible to ligands and a major blue species with rhombic line shape (g1 = 2.21, g2 = 2.06, g3 = 2.03, A1 = 50 x 10(-4) cm-1, A2 = 30 x 10(-4) cm-1, A3 = 76 x 10(-4) cm-1), which is accessible to ligands and participates in redox reactions. The major blue species in cupric horse liver alcohol dehydrogenase is metastable, since it is reduced in a process markedly accelerated in the presence of oxygen or hydrogen peroxide. In addition, the reduction depends on the presence of exogenous metal ligands or coenzymes. Whereas the binary complex enzyme-NAD+ is even more susceptible to bleaching than the free enzyme, the cupric center is stable towards bleaching in the binary complex enzyme-NADH. In the discussion the redox properties and coordination chemistry of Cu2+ in horse liver alcohol dehydrogenase and copper proteins are compared.

摘要

活性位点特异性重构的Cu2+马肝醇脱氢酶（醇：NAD+氧化还原酶，EC 1.1.1.1）的光学光谱和电子顺磁共振（EPR）光谱与天然蓝色铜（1型）蛋白的光谱相似。不同温度和频率下的EPR光谱揭示了铜中心的异质性：一种少量的“非蓝色”物种，具有轴向线形（g平行 = 2.16，g垂直 = 2.04；A平行 = 100×10−4 cm−1），约占总铜量的10%，配体无法接近；以及一种主要的蓝色物种，具有菱形线形（g1 = 2.21，g2 = 2.06，g3 = 2.03，A1 = 50×10−4 cm−1，A2 = 30×10−4 cm−1，A3 = 76×10−4 cm−1），配体可以接近并参与氧化还原反应。马肝醇脱氢酶中主要的蓝色物种是亚稳态的，因为它在有氧气或过氧化氢存在时会在一个明显加速的过程中被还原。此外，还原作用取决于外源金属配体或辅酶的存在。虽然二元复合物酶 - NAD+比游离酶更容易被漂白，但铜中心在二元复合物酶 - NADH中对漂白是稳定的。在讨论中，对马肝醇脱氢酶和铜蛋白中Cu2+的氧化还原性质和配位化学进行了比较。