牛脾胆绿素还原酶的性质

纯牛脾胆绿素还原酶是单一蛋白质,分子量约34 000,等电点约6.2。该酶对胆绿素具有专一性,在还原胆绿素为胆红素中,以还原胆绿素Ⅸ_α最快,Ⅸ_β、Ⅸ_γ和Ⅸ_δ皆很慢。于还原反应中,此酸可以NADH为电子和氢供体,NADPH亦然。然而,NADH依赖性酸与NADPH依赖性酶动力学性质不同:与NADH反应的最适pH7.0,而与HADPH反应时为8.5;两者活性均为过量的胆绿素所抑制,不过,NADPH依赖性酶更敏感。

Properties of Biliverdin Reductase From Cow Spleen

This paper reports the properties of purified biliverdin reductase from cow spleen.It was a monomer protein with a molecular weight of about 34kD.Its isoelectric point was at 6.2 The enzyme was strictly specific to biliverdin and the change of reducing biliverdin IXa to bilirubin IXa was with the maximum velocity among the four biliverdin isomers.The purified enzyme could utilize both NADH and NADPH as electron and hydrogen donors for the reduction of biliverdin.However, there were considerable differences in the kinetic properties of the NADH-dependent and the NADPH-dependcnt biliverdin reductase activities: the pH optimum of the reaction with NADH was 7.0 whereas that of the reaction with NADPH was 8.5; both the NADH-dependent and NADPH-dependent activities were inhibited by excess biliverdin, but this inhibition was far more pronounced in the NADPH system than in the NADH one.