血红素-血红素结合蛋白与一氧化碳的相互作用。

The interaction of heme-hemopexin with CO.

作者信息

Shaklai N, Sharma V S, Muller-Eberhard U, Morgan W T

出版信息

J Biol Chem. 1981 Feb 25;256(4):1544-8.

Abstract

The equilibria and kinetics of the reaction of heme-hemopexin with CO were studied. A stoichiometry of one CO/heme was determined, and the affinity of heme-hemopexin for CO was found to be pH-dependent. At pH 8.0, the affinity constant was 4.5 X 10(5) M-1 compared with 4 X 10(6) M-1 at pH 6.1. The kinetics of CO binding were also pH-dependent. A biphasic reaction at neutral pH could be resolved into a faster phase (kon = 2.2 X 10(3) M-1 s-1) solely found at pH 6.0, and a slower phase (kon = 2.0 X 10(2) M-1 s-1) solely found at pH 8.0. The dissociation reaction on the other hand was found to be independent of pH in the range examined (koff = 5 X 10(-4) s-1).

摘要

研究了血红素-血红素结合蛋白与CO反应的平衡和动力学。确定了化学计量比为一个CO/血红素，并且发现血红素-血红素结合蛋白对CO的亲和力取决于pH值。在pH 8.0时，亲和常数为4.5×10⁵ M⁻¹，而在pH 6.1时为4×10⁶ M⁻¹。CO结合的动力学也取决于pH值。在中性pH下的双相反应可分解为仅在pH 6.0时出现的较快相（正向速率常数kon = 2.2×10³ M⁻¹ s⁻¹）和仅在pH 8.0时出现的较慢相（正向速率常数kon = 2.0×10² M⁻¹ s⁻¹）。另一方面，发现解离反应在所研究的pH范围内与pH无关（逆向速率常数koff = 5×10⁻⁴ s⁻¹）。