牛脾胆绿素还原酶的理化性质

PROPERTIES OF BILIVERDIN REDUCTASE FROM COW SPLEEN

纯牛脾胆绿素还原酶是分子量约34,000的单体蛋白质。该酶对胆绿素具有专一性,在将胆绿素还原为胆红素时,以胆绿素Ⅸα还原最快,Ⅸβ、Ⅸγ和Ⅸδ皆很慢。于还原反应中,此酶可以 NADH 或NADPH 为电子和氢供体,但酶动力学性质不同:与 NADH 或 NADPH 反应的最适 pH 分别为7.0,和8.5;两者活性均为过量的胆绿素所抑制,但后者更为敏感。

The purified biliverdin reductase from cow spleen was a mono- mer protein with a molecular weight of about 34000.The enzyme was specific to biliverdin and reduced biliverdin IX_τ to bilirubin IX_τ with the maximum velo- city among the four biliverdin isomers.The purified enzyme could utilize both NADH and NADPH as electron and hydrogen donors for the reduction of biliver- din.However,there were considerable differences between their kinetic properties: the optimum pH of the reaction with NADH was 7.0 whereas that with NADPH was 8.5;both activities were inhibited by excess biliverdin,but this inhibition was far more pronounced in the latter system