Koren R, Nissani E, Perlmutter-Hayman B
Biochim Biophys Acta. 1982 Apr 21;703(1):42-8. doi: 10.1016/0167-4838(82)90008-5.
The kinetics of the reaction between bilirubin and bovine serum albumin have been re-investigated at 20 degrees C. The results of previous authors concerning both human and bovine serum albumin were largely confirmed, namely the existence of two first-order configurational changes after a primary complex is formed in a fast, bimolecular step. From the kinetic behaviour it is concluded that this primary complex is present in non-negligible concentration after equilibrium is reached, and that it exchanges bilirubin with the surroundings with a rate constant of at least 23 s-1. This also means that the secondary complex, and, possible, also the final product, are in dynamic equilibrium with each other and with the primary complex, and, therefore, only the sum of their formation and dissociation rate constants can be measured. The dependence of the two observable relaxation times on pH does not parallel the N leads to B transition. On the other hand, a pH jump between 7.4 and 9.0 is assumed to monitor the N leads to B transition, both the free albumin and the complex in its various forms undergoing this transition at identical rates. This transition, although influencing the absorptivity of the complex, was found not to influence the strength of the binding site.
已在20℃下重新研究了胆红素与牛血清白蛋白之间反应的动力学。先前关于人血清白蛋白和牛血清白蛋白的作者的结果在很大程度上得到了证实，即在快速的双分子步骤中形成初级复合物后存在两个一级构型变化。从动力学行为可以得出结论，在达到平衡后，这种初级复合物以不可忽略的浓度存在，并且它与周围环境交换胆红素的速率常数至少为23 s-1。这也意味着二级复合物以及可能的最终产物彼此之间以及与初级复合物处于动态平衡，因此，只能测量它们形成和解离速率常数的总和。两个可观察到的弛豫时间对pH的依赖性与N到B的转变不平行。另一方面，假定在7.4和9.0之间的pH跃变来监测N到B的转变，游离白蛋白和各种形式的复合物都以相同的速率经历这种转变。尽管这种转变影响复合物的吸光度，但发现它不影响结合位点的强度。
