Kinetics and mechanism of bilirubin binding to human serum albumin.
Kinetics and mechanism of bilirubin binding to human serum albumin.
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胆红素与人血清白蛋白结合的动力学和机制。
DOI：
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发表时间：
1978
影响因子：
4.8
通讯作者：
S. Stroupe
中科院分区：
文献类型：
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作者：
R. Gray;S. Stroupe
通过监测胆红素吸光度的变化，研究了在pH 7.40，4℃时，胆红素与人血清白蛋白结合的动力学。在380 nm处的吸光度变化的时间过程是复杂的：至少检测到三个动力学事件，包括双分子缔合(K1=3.8+/-2.0×10(7)M-1 S-1)和两个弛豫步骤(52=40.2+/-9.4S-1和K3=3.8+/-0.5 S-1)。在含有过量白蛋白的准一级条件下，证实了这两个慢弛豫的存在。曲线拟合程序允许将吸收系数分配给中间物种。当在420 nm处观察到胆红素-白蛋白结合动力学时，只观察到两个弛豫；显然二级缔合步骤在该波长是等色散的。通过将预先平衡的人白蛋白-胆红素复合体与牛白蛋白混合来测量白蛋白结合胆红素的解离率。在485 nm波长处测得的胆红素解离速率常数为k-3=0.01 S-1。因此，由k1/k-3比值确定的胆红素与人血清白蛋白结合的平衡常数的最小值约为4×10(9)M-1。
The kinetics of bilirubin binding to human serum albumin at pH 7.40, 4 degrees C, was studied by monitoring changes in bilirubin absorbance. The time course of the absorbance change at 380 nm was complex: at least three kinetic events were detected including the bimolecular association (k1 = 3.8 +/- 2.0 X 10(7) M-1 S-1) and two relaxation steps (52 = 40.2 +/- 9.4 s-1 and k3 = 3.8 +/- 0.5 s-1). The presence of the two slow relaxations was confirmed under pseudo-first order conditions with excess albumin. Curve-fitting procedures allowed the assignment of absorption coefficients to the intermediate species. When the bilirubin-albumin binding kinetics was observed at 420 nm, only the two relaxations were seen; apparently the second order association step was isosbestic at this wavelength. The rate of albumin-bound bilirubin dissociation was measured by mixing the pre-equilibrated human albumin-bilirubin complex with bovine albumin. The rate constant for bilirubin dissociation measured at 485 nm was k-3 = 0.01 s-1 at 4 degrees C. A minimum value of the equilibrium constant for bilirubin binding to human albumin determined from the ratio k1/k-3 is therefore approximately 4 X 10(9) M-1.