Yip L C, Roome S, Balis M E
Biochemistry. 1978 Aug 8;17(16):3286-91. doi: 10.1021/bi00609a017.
Upon storage, human erythrocyte phosphoribosyl pyrophosphate synthetase (PRibPP synthetase, EC 2.7.6.1) from normal individuals was found to undergo a spontaneous dissociation into active enzyme components of much smaller molecular mass (60 000--90 000). These modified forms of enzyme exhibit kinetic properties different from the original large molecular weight enzyme (over 200 000). The small active components can be reversibly associated to form larger molecules in the presence of purine ribonucleotides as well as phosphoribosyl pyrophosphate (PRibPP). ATP was found to be most effective in associating PRibPP synthetase, while guanylate nucleotides seem to have no effect. The large molecular weight components, once separated from the milieu, were not able to undergo further dissociation. Fresh or stored human white cell tissue homogenates were found to lack the low-molecular-weight enzyme under all our experimental conditions. A characteristic enzyme modification similar to that observed in stored erythrocyte was also noted in erythrocytes of increasing ages. The physiological significance of these findings to the regulatory function of PRibPP synthetase in purine metabolism in vivo is discussed.
在储存过程中，发现来自正常个体的人红细胞磷酸核糖焦磷酸合成酶（PRibPP合成酶，EC 2.7.6.1）会自发解离成分子量小得多（60000 - 90000）的活性酶组分。这些酶的修饰形式表现出与原始大分子酶（超过200000）不同的动力学特性。在嘌呤核糖核苷酸以及磷酸核糖焦磷酸（PRibPP）存在的情况下，小的活性组分可以可逆地结合形成更大的分子。发现ATP在使PRibPP合成酶结合方面最有效，而鸟苷酸核苷酸似乎没有作用。一旦与周围环境分离，大分子组分就无法进一步解离。在我们所有的实验条件下，发现新鲜或储存的人白细胞组织匀浆缺乏低分子量酶。在年龄不断增加的红细胞中也观察到了与储存红细胞中类似的特征性酶修饰。讨论了这些发现对PRibPP合成酶在体内嘌呤代谢调节功能的生理学意义。
