Formation and photolability of low-spin ferrous cytochrome c peroxidase at alkaline pH.
Formation and photolability of low-spin ferrous cytochrome c peroxidase at alkaline pH.
复制标题
碱性 pH 下低自旋亚铁细胞色素 c 过氧化物酶的形成和光稳定性。
DOI：
10.1021/bi00118a032
复制
发表时间：
1992
期刊：
影响因子：
2.9
通讯作者：
Ondrias,MR
中科院分区：
文献类型：
--
作者：
Wang,JL;Boldt,NJ;Ondrias,MR
新墨西哥州，阿尔伯克基，新墨西哥州，87131，1991年6月14日接收; 1991年10月10日接收的修订版手册摘要：已知天然细胞色素c过氧化物酶（CCP）的亚铁形式在pH 7.00-9.70范围内滴定时发生可逆转变。这种过渡产生从五配位高自旋到六配位低自旋血红素活性位点的转换，并且在血红素光学吸收光谱中清楚地显而易见。在这里，我们报告的特点，这种过渡和它的影响后，当地血红素环境使用各种光学光谱。六配位低自旋血红素的形成被解释为涉及His-52在远端位点的结合后，广泛的氢键网络内和周围的血红素口袋的CCP（II）在alkalinepH的扰动。有趣的是，在远紫外和Soret区域的CCP（II）的CD调查表明，一个单一的高自旋物种的消失和存在的至少两个低自旋物种的CCP（II）的pH值升高到7.90以上。此外，瞬态共振拉曼实验表明，六配位低自旋物种可以在10 ns的激光脉冲内光解，产生一种类似于低pH值（高自旋）形式的CCP（II）在碱性pH值的物种。然而，光解的程度是相当依赖于pH值，在pH= 8.50的最大光解产率。
Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131 Received June 14, 1991; Revised Manuscript Received October 10, 1991 abstract: The ferrous form of native cytochrome c peroxidase (CCP) is known to undergo a reversible transition when titrated over the pH range of 7.00-9.70. This transition produces a conversion from a pentacoordinate high-spin to a hexacoordinate low-spin heme active site and is clearly apparent in the heme optical absorption spectra. Here, we report the characterization of this transition and its effect upon the local heme environment using various optical spectroscopies. The formation of hexacoordinate low-spin heme is interpreted to involve the binding of His-52 at the distal site after the perturbation of the extensive H-bonded network within and around the heme pocket of CCP (II) at alkalinepH. Interestingly, CD investigations of CCP (II) in the far-UV and Soret regions indicate the dissappearance of a single high-spin species and the existence of at least two low-spin species of CCP (II) as the pH is raised above 7.90. Furthermore, transient resonance Raman experiments demonstrate that the hexacoordinate low-spin species can be photolyzed within 10-ns laser pulses, producing a species similar to the low-pH (high-spin) form of CCP (II) at alkaline pH. However, the extent of photolysis is quite pH dependent, with a maximum photodissociation yield at pH= 8.50.