PURINE METABOLISM IN SCHISTOSOMA MANSONI

比较生化研究的潜在好处之一是 寄生虫是识别代谢缺陷的后者和 利用这些漏洞进行抗寄生虫化疗。 我们最近证实没有嘌呤的从头合成。 曼氏血吸虫中的核苷酸，并对嘌呤进行了描述 在这种有机体中的打捞途径。我们的结果表明 次黄嘌呤-鸟嘌呤磷酸核糖转移酶(HGPRT)作为一种 曼氏链霉菌回收嘌呤的关键酶；一种有效的 抑制这种酶会导致寄生虫的死亡。我们有 因为将这种酶纯化到明显的同质性，部分表征了 它发现它的许多特性与哺乳动物的特性不同 HGPRT；因此提高了选择性抑制寄生虫的可能性 HGPRT。我们未来的研究计划要求：(1)寻找具体的和 曼氏沙门氏菌HGPRT的有效抑制剂及其可能的用途 抗血吸虫药物；(2)曼氏血吸虫HGPRT基因c-DNA的克隆 并将其限制性内切酶图谱和核苷酸序列与已知 哺乳动物HGPRT的氨基酸序列可能存在的蛋白质差异 (3)克隆沙门氏菌c-DNA全长序列。 Mansoni HGPRT.这将通过引入一个特殊的 构建表达载体载体转化大肠杆菌#165菌株 在黄嘌呤-鸟嘌呤磷酸核糖转移酶(XGPRT)中缺失 表达；或通过引入构建于 逆转录病毒LTR嵌合质粒导入哺乳动物HGPRT细胞系并 曼氏葡萄球菌HGPRT在HAT培养基中表达条件的筛选原住民 通过这些方法大量生产的曼氏葡萄球菌HGPRT将 有助于更彻底地调查 (4)克隆编码曼氏血吸虫HGPRT和HGPRT的基因组DNA 将其全长、限制性内切酶图谱和核苷酸序列与 用于寻找可能的内含子的全长曼氏链球菌HGPRT c-DNA 基因结构和基因两侧的任何调控片段 为了更好地了解曼氏血吸虫HGPRT的遗传调控。我们有 还在曼氏链霉菌中鉴定出一种结节蛋白激酶，它具有独特的 底物特异性，是强效抗血吸虫药物的靶点 杀瘤蛋白的活性。我们计划进一步将这种酶描述为一种 可能成为抗血吸虫化疗的靶点。

One of the potential benefits of comparative biochemical studies of parasites is the identification of metabolic deficiencies in the latter and the exploitation of these vulnerabilities for antiparasitic chemotherapy. We have recently verified the absence of de novo synthesis of purine nucleotides in Schistosoma mansoni and proceeded to delineate the purine salvage pathways in this organism. Our results pointed to hypoxanthine-guanine phosphoribosyl transferase (HGPRT) as one of the pivotal enzymes in the purine salvage by S. mansoni; an effective inhibition of this enzyme would lead to death of the parasite. We have since purified this enzyme to apparent homogeneity, partially characterized it and found many of its properties differ from those of the mammalian HGPRT; thus raising the possibility of selective inhibition of the parasite HGPRT. Our future research plan calls for; (1) searching for specific and potent inhibitors of S. mansoni HGPRT and pursuing their possible use as antischistosomal agents; (2) cloning the c-DNA encoding S. mansoni HGPRT and comparing its restriction map and nucleotide sequences with the known amino acid sequence of mammalian HGPRT for possible differences in protein structures between the two enzymes; (3) cloning the full-length c-DNA of S. mansoni HGPRT. This will be done either by introducing a specially constructed expression vector plasmid into an Escherichia coli #165 strain deleted in xanthine-guanine phosphoribosyl transferase (XGPRT) for expression; or by introducing a c-DNA library of S. mansoni constructed in retroviral LTR chimeric plasmids into a mammalian HGPRT cell line and selecting for the expression of S. mansoni HGPRT in HAT medium. The native S. mansoni HGPRT thus produced in larger quantities by these methods will facilitate more thorough investigations on the kinetic and structural of the enzyme; (4) cloning the genomic DNA encoding S. mansoni HGPRT and comparing its full size, restriction pattern and nucleotide sequences with the full-length S. mansoni HGPRT c-DNA to search for possible introns in the gene structure and any regulatory segments flanking the gene in order to better understand the genetic regulation of S. mansoni HGPRT. We have also identified a tubercidin kinase in S. mansoni which has a unique substrate specificity and is the target of the potent antischistosomal activity of tubercidin. We plan to further characterize this enzyme as a potential target for antischistosomal chemotherapy.