Hofmann O, Brittain T
Biochemistry and Molecular Biology Research Group, School of Biological Sciences, University of Auckland, New Zealand.
Biochem J. 1996 Apr 1;315 ( Pt 1)(Pt 1):65-70. doi: 10.1042/bj3150065.
The three human embryonic haemoglobins have been studied using a range of stopped-flow and flash photolysis experiments. The association and dissociation kinetics and equilibrium constants for the tetramer-dimer reactions of the deoxy and oxygenated forms have been investigated and found to be characterized by constants similar to those of the human adult protein. The rates of oxygen dissociation from the embryonic haemoglobins have been measured and appear to be responsible for the high oxygen-binding affinity associated with the embryonic proteins compared with the adult protein. The pH dependence of the oxygen dissociation rate constants also accounts for the rather unusual, previously described, Bohr effects characteristic of the embryonic haemoglobins. A general scheme has been developed coupling both the dimer-tetramer equilibria and ligand-binding steps observed following photolysis of the liganded forms of the human embryonic haemoglobins.
利用一系列停流和闪光光解实验对三种人类胚胎血红蛋白进行了研究。研究了脱氧和氧合形式的四聚体 - 二聚体反应的缔合和解离动力学及平衡常数，发现其特征常数与人类成人血红蛋白的相似。已测量了胚胎血红蛋白的氧解离速率，与成人血红蛋白相比，该速率似乎是胚胎血红蛋白具有高氧结合亲和力的原因。氧解离速率常数对pH的依赖性也解释了胚胎血红蛋白先前描述的相当不寻常的玻尔效应特征。已制定了一个通用方案，将人类胚胎血红蛋白配体形式光解后观察到的二聚体 - 四聚体平衡和配体结合步骤联系起来。
