Ruoslahti E, Estes T, Seppäla M
Biochim Biophys Acta. 1979 Jun 19;578(2):511-9. doi: 10.1016/0005-2795(79)90181-8.
alpha-Fetoprotein, a fetal protein associated with certain tumors, was found to bind bilirubin. Addition of human or bovine alpha-fetoprotein to bilirubin solutions enhanced the light absorbance of bilirubin and shifted its maximum. Bovine alpha-fetoprotein caused a marked shift towards shorter wavelengths, while human alpha-fetoprotein gave a slight red shift. The spectral changes were used to study the characteristics of the binding of bilirubin by bovine alpha-fetoprotein. These studies indicated the presence of one binding site/molecule of alpha-fetoprotein with an association constant of about 1.1 . 10(6) M-1. A difference between the spectral changes brought about by alpha-fetoprotein and albumin allowed comparison of their relative affinities for bilirubin. The spectrum approximated the average between the spectra induced by the two proteins when the ratio of bovine alpha-fetoprotein to bovine albumin was 6.3 : 1, and of the human proteins 21 : 1, respectively. These results show that alpha-fetoprotein from two species binds bilirubin with an affinity somewhat lower than that of albumin. Binding of bilirubin by alpha-fetoprotein is in agreement with the recent demonstration of structural homology between alpha-fetoprotein and albumin. Whether alpha-fetoprotein plays a role in the metabolism of bilirubin or other degradation products of heme remains to be investigated.
甲胎蛋白，一种与某些肿瘤相关的胎儿蛋白，被发现可结合胆红素。向胆红素溶液中添加人或牛的甲胎蛋白可增强胆红素的吸光度并使其最大吸收峰发生位移。牛甲胎蛋白导致明显向较短波长的位移，而人甲胎蛋白则产生轻微的红移。利用光谱变化来研究牛甲胎蛋白与胆红素结合的特性。这些研究表明甲胎蛋白分子存在一个结合位点，其缔合常数约为1.1×10⁶ M⁻¹。甲胎蛋白和白蛋白引起的光谱变化之间的差异使得能够比较它们对胆红素的相对亲和力。当牛甲胎蛋白与牛白蛋白的比例为6.3:1以及人甲胎蛋白与人白蛋白的比例为21:1时，光谱近似于由这两种蛋白质诱导的光谱的平均值。这些结果表明来自两个物种的甲胎蛋白结合胆红素的亲和力略低于白蛋白。甲胎蛋白与胆红素的结合与最近关于甲胎蛋白和白蛋白之间结构同源性的证明相一致。甲胎蛋白是否在胆红素或血红素的其他降解产物的代谢中起作用仍有待研究。
