PURINE/PYRIMIDINE METABOLISM IN TRICHOMONAS AND GIARDIA

三种厌氧原生动物寄生虫，蓝氏贾第鞭毛虫，阴道毛滴虫 和胎滴虫，它们都是通过附着在宿主上自然生长的 上皮细胞和吞噬功能，已被发现缺乏 嘌呤和嘧啶核苷酸从头合成的能力和 二氢叶酸还原酶和胸苷合成酶缺乏 活动。它们依赖于相当简单的嘌呤回收途径， 嘧啶和核苷。这些小路，由我们在 在过去的两年里，我提出了几种关键的酶，这些酶不仅是 对这些寄生虫的生存是必不可少的，但也表现出独特的底物 使自己有资格成为抗寄生虫的潜在目标的特异性 化疗。这些酶是革兰氏原虫中的APRT、GPRT和UPRT， 胎儿绒毛虫HXGPRT、UPRT和IMPDH与脱氧核糖核苷 阴道毛滴虫磷酸转移酶。GPRT、HXGPRT和IMPDH已被 纯化到同质，并显示出许多不同的性质 相关的宿主酶。我们正在计划一个放映节目， 这些分离酶的抑制剂是寻找化疗药物的一种方法 探员们。另一方面，我们将制备兰氏革兰氏菌GPRT的纯样品， 胎儿弓形虫HXGPRT、胎儿弓形虫IMPDH和小鼠肉瘤180 IMPDH微克数 按既定程序确定数量。的N-末端序列 将测定四种纯化的酶，相应的 寡核苷酸将被合成并用作探针，开始 编码这些基因的鉴定、克隆和测序 用于序列比较的酶。预计该序列 与酶活性部位相关的差异可以解释 不同的底物特性，并有助于新药设计。同时， UPRT和阴道毛滴虫的进一步净化 脱氧核糖核苷磷酸转移酶将用亲和层析柱进行追踪 色谱图。一次令人兴奋的观察，发现了一个 在阴道毛滴虫中发现了双链RNA，在阴道毛滴虫中发现了RNA基因。 阴道线虫DNA及其与RNA之间可能的关系 阴道毛滴虫对甲硝唑的敏感性将引领我们进一步追求 这些新的发现。阴道毛滴虫基因组文库将被 并且双链RNA将被用作探针来启动 其编码序列的鉴定、克隆及序列测定 基因组以进一步了解该基因的生物学功能 双链RNA。

Three anaerobic protozoan parasites, Giardia Lamblia, Trichomonas vaginalis and Tritrichomonas foetus, which all grow naturally by adhering to host epithelial cells and performing phagocytosis, have been found lacking the capability of de novo synthesis of purine and pyrimidine nucleotides and deficient in dihydrofolate reductase and thymidylate synthetase activities. They depend on rather simple salvage pathways for purines, pyrimidines and nucleosides. These pathways, delineated by us during the past two years, have presented several pivotal enzymes which not only are essential for survival of these parasites but also exhibit unique substrate specificities qualifying themselves as potential targets of antiparasitic chemotherapy. These enzymes are the APRT, GPRT and UPRT in G. lamblia, HXGPRT, UPRT and IMPDH in T. foetus and the deoxyribonucleoside phosphotransferase of T. vaginalis. The GPRT, HXGPRT and IMPDH have been purified to homogeneity and shown to have many different properties from the related host enzymes. We are planning on a screening program for inhibitors of these isolate enzymes as one way of finding chemotherapeutic agents. On the other hand we will prepare pure samples of G. lamblia GPRT, T. foetus HXGPRT, T. foetus IMPDH and mouse sarcoma 180 IMPDH in microgram quantities by the established procedures. The N-terminal sequences of the four purified enzymes will be determined, the corresponding oligonucleotides will be synthesized and used as probes to begin identifications, clonings and sequencings of the genes encoding these enzymes for sequence comparisons. It is anticipated that sequence differences associated with the enzyme active sites may explain the different substrate specificities and help new drug designs. Meanwhile, further purifications of the UPRT's and the T. vaginalis deoxyribonucleoside phosphotransferase will be pursued with affinity column chromatographies. An exciting observation of the presence of a double-stranded RNA in T. vaginalis, the discovery of the RNA gene in T. vaginalis DNA and the possible relationship between the RNA and the metronidazole-sensitivity of T. vaginalis will lead us into further pursue of these new findings. Genomic libraries of T. vaginalis will be established and the double-stranded RNA will be used as a probe to initiate the identification, cloning and sequence determination of its encoding genome for further understanding of the biological function of the double-stranded RNA.