Steady-state kinetics of the schistosomal hypoxanthine-guanine phosphoribosyltransferase.
Steady-state kinetics of the schistosomal hypoxanthine-guanine phosphoribosyltransferase.
复制标题
血吸虫次黄嘌呤鸟嘌呤磷酸核糖转移酶的稳态动力学。
DOI：
10.1021/bi00118a024
复制
发表时间：
1992
期刊：
影响因子：
2.9
通讯作者：
Wang,CC
中科院分区：
文献类型：
--
作者：
Yuan,L;Craig3rd,SP;McKerrow,JH;Wang,CC
摘要：血吸虫病是一种感染约2亿人的寄生虫病。主要病原曼氏血吸虫的次黄嘌呤-鸟嘌呤磷酸核糖基转移酶（HGPRTase）已被提出作为抗血吸虫化疗的潜在靶点[Dovey， H. F., McKerrow， J. H., & Wang, CC (1984) Mol. Biochem.。中华寄生虫病杂志，11(1),167 -167。在相同条件下，将次黄嘌呤和鸟嘌呤同时加入血吸虫HGPRTase的正反反应中，确定了血吸虫HGPRTase的稳态动力学机制。在一种底物的一系列固定浓度下，初始速度与另一种底物浓度的双倒数图给出了一组相交的直线，表明血吸虫hgprtase催化反应的顺序机制。在产物抑制研究中，结果表明焦磷酸镁（MgPPi）对焦磷酸二镁（Mg2PRPP）、次黄嘌呤和鸟嘌呤是一种非竞争性抑制剂。此外，单磷酸肌苷镁（MgIMP）和单磷酸鸟苷镁（MgGMP）分别是次黄嘌呤和鸟嘌呤的非竞争性抑制剂，但对Mg2PRPP是竞争性抑制剂。此外，Mg2PRPP是MgIMP和MgGMP的竞争性抑制剂，但对MgPPi是非竞争性抑制剂。符合实验数据的最小动力学模型是有序的bi-bi机制，其中底物以确定的顺序与酶结合（首先是Mg2PRPP，然后是嘌呤碱基），而产物按顺序释放（首先是mgpp，然后是MgIMP或MgGMP）。血吸虫酶产物的有序释放显然不同于报道的人类HGPRTase产物的快速平衡随机释放方式[Giacomello， A., & Salerno， C.(1978) J. Biol.]。化学学报，2011,31(3):638 - 644。这些结果表明，设计一种高度特异性的血吸虫HGPRTase抑制剂，它只与酶-嘌呤核苷酸二元复合物结合，是可能的。
Revised Manuscript Received October 15, 1991 abstract: Schistosomiasis isa trematode infectionof some 200 million people. Thehypoxanthine-guanine phosphoribosyltransferase (HGPRTase) of the major etiologic agent, Schistosoma mansoni, has been proposed as a potential target for antischistosomal chemotherapy [Dovey, H. F., McKerrow, J. H., & Wang, CC (1984) Mol. Biochem. Parasitol. 11, 157-167]. The steady-state kinetic mechanism for the schistosomal HGPRTase has been determined by including both hypoxanthine and guanine in the forward and reverse reactions under identical conditions. Double-reciprocal plots of initial velocity versus the concentration of one substrate, at a series of fixed concentrations of the other, give groups of intersecting straight lines indicating a sequential mechanism for the schistosomal HGPRTase-catalyzed reactions. In product inhibition studies, the results show that magnesium pyrophosphate (MgPPi) is a noncompetitive inhibitor with respect to dimagnesium phosphoribose pyrophosphate (Mg2PRPP), hypoxanthine, and guanine. Also, magnesium inosine monophosphate (MgIMP) and magnesium guanosine monophosphate (MgGMP) are noncompetitive inhibitors with respect to hypoxanthine or guanine, respectively, but are competitive inhibitors to Mg2PRPP. Furthermore, Mg2PRPP is a competitive inhibitor with respect to MgIMP and MgGMP but is a non-competitive inhibitor to MgPPi. The minimum kinetic model which fits the experimental data is an ordered bi-bi mechanism, where the substrates bind to the enzyme in a defined order (first Mg2PRPP followed by the purine bases), while products are released in sequence (first MgPPifollowed by MgIMP or MgGMP). The ordered release of products of the schistosomal enzyme apparently is different from that reported for the human HGPRTase in which the release of products is in rapid equilibrium random fashion [Giacomello, A., & Salerno, C.(1978) J. Biol. Chem. 253, 6038-6044]. These results suggest that the design of a highly specific inhibitor of the schistosomal HGPRTase, which binds exclusively to the enzyme-purine nucleotide binary complex, may be possible.