Robinson A K, Barnes L D
Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760.
Biochem J. 1991 Oct 1;279 ( Pt 1)(Pt 1):135-9. doi: 10.1042/bj2790135.
Phenylglyoxal, a reagent with high specificity for arginine residues, inactivated Ap4A phosphorylase I from Saccharomyces cerevisiae in a pseudo-first-order manner. The second-order rate constant was 11.5 +/- 2.5 M-1 min-1. The loss of activity was a linear function of the incorporation of [7-14C]phenylglyoxal. The incorporation of 1.9 +/- 0.4 mol of phenylglyoxal/mol of enzyme accounted for complete loss of activity. The specificity of inactivation by phenylglyoxal was tested in the presence of ApnA (n = 2-6), ADP, ATP and Pi. The substrates, Ap4A, Ap5A and Pi protected the enzyme against inactivation, but Ap2A, Ap3A and Ap6A did not. Ap4A, Ap5A and Pi reduced the rate of inactivation by about 70%, 60% and 37% respectively. The Ap4A phosphorolysis products, ADP and ATP, also partially protected the enzyme against inactivation by phenylglyoxal. Thus Ap4A phosphorylase I probably contains an arginine residue in the binding site for Ap4A.
苯乙二醛是一种对精氨酸残基具有高特异性的试剂，它以假一级反应方式使来自酿酒酵母的Ap4A磷酸化酶I失活。二级反应速率常数为11.5±2.5 M⁻¹ min⁻¹。活性丧失是[7-¹⁴C]苯乙二醛掺入量的线性函数。每摩尔酶掺入1.9±0.4摩尔苯乙二醛导致活性完全丧失。在ApnA（n = 2 - 6）、ADP、ATP和Pi存在的情况下测试了苯乙二醛失活的特异性。底物Ap4A、Ap5A和Pi可保护该酶不被失活，但Ap2A、Ap3A和Ap6A则不能。Ap4A、Ap5A和Pi分别使失活速率降低约70%、60%和37%。Ap4A磷酸解产物ADP和ATP也部分保护该酶不被苯乙二醛失活。因此，Ap4A磷酸化酶I在Ap4A结合位点可能含有一个精氨酸残基。
