大肠埃希菌K-12肌苷-鸟苷磷酸化酶的纯化及性质研究。
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Koszalka GW, Vanhooke J, Short SA, Hall WW
大肠埃希菌K-12肌苷-鸟苷磷酸化酶的纯化及性质研究。
细菌学杂志，1988年8月;170(8):3493-8。
- PubMed ID
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3042752 (PubMed视图］
- 摘要
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一种黄嘌呤诱导酶，肌苷-鸟苷磷酸化酶，已经从一株缺乏脱氧嘌呤核苷磷酸化酶的大肠杆菌K-12中部分纯化出来。肌苷-鸟苷磷酸化酶的颗粒质量为180千达尔顿，可被对氯苯磺酸(p-CMB)快速灭活。肌苷(Ino)、2′-脱氧肌苷(dIno)、次黄嘌呤(Hyp)、Pi或α -d -核糖-1-磷酸(Rib-1-P)对酶的失活没有保护作用。将失活酶与二硫苏糖醇孵育可恢复其催化活性。与p-CMB反应不影响颗粒质量。肌苷鸟苷磷酸化酶比嘌呤核苷磷酸化酶对热失活更敏感。在45℃pH值5 - 8之间测定的半衰期为5 - 9分钟。磷酸盐(20 mM)使酶热失活稳定，而Ino (1 mM)、dIno (1 mM)、xanthosin (Xao) (1 mM)、Rib-1-P (2 mM)或Hyp (0.05 mM)没有影响。然而，在1 mM处的Hyp确实稳定了酶。此外，Pi (20 mM)和Hyp (0.05 mM)的组合比Pi单独使用更能稳定该酶。磷解方向和合成方向的表观活化能分别为11.5 kcal/mol和7.9 kcal/mol。 The pH dependence of Ino cleavage or synthesis did not vary between 6 and 8. The substrate specificity, listed in decreasing order of efficiency (V/Km), was: 2'-deoxyguanosine, dIno, guanosine, Xao, Ino, 5'-dIno, and 2',3'-dideoxyinosine. Inosine-guanosine phosphorylase differed from the deo operon-encoded purine nucleoside phosphorylase in that neither adenosine, 2'-deoxyadenosine, nor hypoxanthine arabinoside were substrates or potent inhibitors. Moreover, the E. coli inosine-guanosine phosphorylase was antigenically distinct from the purine nucleoside phosphorylase since it did not react with any of 14 monoclonal antisera or a polyvalent antiserum raised against deo-encoded purine nucleoside phosphorylase.