Johnson G G, Nash S A
Biochem Genet. 1983 Apr;21(3-4):213-26. doi: 10.1007/BF00499134.
We have previously given evidence that the hypoxanthine-guanine phosphoribosyltransferase (HGPRT; EC 2.4.2.8) isozymes in human erythroid cells result from posttranslational modifications of a single gene product [Johnson, G. G., et al. (1982). Biochemistry 21: 960]. In the present work we compare the properties of the unmodified and two major modified isozymes, which collectively account for 90% of the HGPRT enzyme activity in cell lysates. The modified isozymes differ from the parent molecule in the pH dependence of activity and in the relative utilization of the two purine base substrates, hypoxanthine and guanine. In contrast to the changes in the catalytic properties of the enzyme, the modifications have no detectable effects on the heat stability or on the equilibrium between enzyme dimers and enzyme tetramers.
我们之前已经提供证据表明，人类红细胞中的次黄嘌呤 - 鸟嘌呤磷酸核糖转移酶（HGPRT；EC 2.4.2.8）同工酶是由单一基因产物的翻译后修饰产生的[约翰逊，G.G.等人（1982年）。《生物化学》21: 960]。在本研究中，我们比较了未修饰的同工酶和两种主要修饰同工酶的特性，它们共同占细胞裂解物中HGPRT酶活性的90%。修饰后的同工酶在活性的pH依赖性以及两种嘌呤碱基底物次黄嘌呤和鸟嘌呤的相对利用方面与亲本分子不同。与酶催化特性的变化相反，这些修饰对热稳定性或酶二聚体与酶四聚体之间的平衡没有可检测到的影响。
