Yun C H, Ahn T, Guengerich F P
Department of Biochemistry, Pai-Chai University, Taejon, 302-735, Korea.
Arch Biochem Biophys. 1998 Aug 15;356(2):229-38. doi: 10.1006/abbi.1998.0759.
A stimulatory effect of increased salt concentration on the enzymatic activity of rat liver microsomes and a reconstituted system containing cytochrome P450 (P450) 2B1 and NADPH-P450 reductase was seen. Structural change of P450 2B1 accompanying the salt-induced increase in its enzyme activity was investigated by circular dichroism, fluorescence spectroscopy, and absorption spectroscopy. It was found that the salt increased alpha-helix content of P450 2B1 in the presence as well as in the absence of a phospholipid. Intrinsic fluorescence emissions also increased with increasing salt concentration. The low-spin iron configuration of P450 2B1 shifted toward the high-spin configuration in response to the increased salt concentration. It was found that the activity increase of P450 coincides with the raised alpha-helix content. The presence of phospholipid magnified this effect. It is proposed that the interaction with salts and phospholipid molecules surrounding P450 2B1 in the endoplasmic reticulum is important for a functional conformation of P450 2B1 in a monooxygenase system including NADPH-P450 reductase.
研究发现，盐浓度升高对大鼠肝脏微粒体以及包含细胞色素P450（P450）2B1和NADPH - P450还原酶的重组系统的酶活性具有刺激作用。通过圆二色性、荧光光谱和吸收光谱研究了伴随盐诱导的酶活性增加，P450 2B1的结构变化。结果发现，无论有无磷脂存在，盐都会增加P450 2B1的α - 螺旋含量。随着盐浓度的增加，内在荧光发射也会增加。响应盐浓度的增加，P450 2B1的低自旋铁构型向高自旋构型转变。研究发现，P450活性的增加与α - 螺旋含量的升高相一致。磷脂的存在放大了这种效应。有人提出，在内质网中，与围绕P450 2B1的盐和磷脂分子的相互作用对于包括NADPH - P450还原酶的单加氧酶系统中P450 2B1的功能构象很重要。
