苯巴比妥诱导的大鼠肝脏微粒体细胞色素P-450与一氧化碳结合及解离的动力学

Kinetics of CO binding to and dissociation from microsomal cytochrome P-450 induced by phenobarbital in rat liver.

作者信息

Gray R D

出版信息

J Biol Chem. 1978 Jun 25;253(12):4364-9.

Abstract

The kinetics of CO binding to hepatic microsomes from phenobarbital-treated Sprague-Dawley rats, measured by stopped flow spectrophotometry, can be resolved into three components with second order velocity constants of 2.23 +/- 0.35 X 10(5) M-1 S-1, 1.59 +/- 0.18 X 10(6) M-1 S-1, and 8.7 +/- 1.7 X 10(6) M-1 S-1. The three CO-binding species were present in ratios of 1:1.25:1.39 as judged by the relative amplitude of the change in absorbance at 450 nm associated with each of the kinetic components. Similar results were obtained in a range of [CO] from 10 to 700 micron when CO recombination was followed subsequent to flash photolysis of the CO-associated microsomes. In contrast, the dissociation rate of CO from its cytochrome P-450 complex measured by the NO replacement method was biphasic. Approximately 40% of the bound CO dissociated at a rate of 0.40 +/- 0.071 s-1, whereas the remaining 60% dissociated at a rate of 0.049 +/- 0.008 s-1 at 20 degrees C.

摘要

通过停流分光光度法测量，苯巴比妥处理的斯普拉格-道利大鼠肝微粒体与一氧化碳（CO）结合的动力学可分解为三个组分，其二阶速度常数分别为2.23±0.35×10⁵ M⁻¹ s⁻¹、1.59±0.18×10⁶ M⁻¹ s⁻¹和8.7±1.7×10⁶ M⁻¹ s⁻¹。根据与每个动力学组分相关的450 nm处吸光度变化的相对幅度判断，这三种与CO结合的物种的比例为1:1.25:1.39。当在CO相关微粒体的闪光光解后跟踪CO重组时，在10至700微米的[CO]范围内获得了类似的结果。相比之下，通过NO替代法测量的CO从其细胞色素P-450复合物中的解离速率是双相的。在20℃时，约40%的结合CO以0.40±0.071 s⁻¹的速率解离，而其余60%以0.049±0.008 s⁻¹的速率解离。