3-D STRUCTURES OF URIDINE & THYMIDINE PHOSPHORYLASES

目的是确定三维结构的 尿苷磷酸化酶和胸苷磷酸化酶。 的 嘧啶磷酸化酶可能负责降解 某些核苷类似物的潜在化疗 值 有人认为嘧啶磷酸化酶 抑制剂可用作化疗剂， 增强嘧啶核苷类似物的功效，或通过 干扰嘧啶碱基补救。 此外该 嘧啶磷酸化酶已被用于酶促 核苷类似物的实验室合成方法。 的 最终目标是提供精确的结构数据， 用两种可能的方式。 一种方法是引导努力， 合成哺乳动物酶的新抑制剂。 第二 方法是提出结构上的修改， 特异性和稳定性。大肠杆菌的酶， 有用的合成工具。 这样的修改可以 使用基因工程的标准技术。 单晶 X射线衍射方法将用于确定晶体 尿苷磷酸化酶和胸苷磷酸化酶的结构。 这两种酶的晶体来自E.大肠杆菌已经生长， 适用于高分辨率晶体衍射分析。 的 结构将使用多晶型- 替换技术，并使用测得的强度数据进行改进 用振荡摄影和同步辐射。 一旦 结构是已知的，活性位点的特征在于： 检测底物、底物类似物和抑制剂复合物， 酶。 希望高分辨率的结构， 尿苷磷酸化酶和胸苷磷酸化酶将提供 了解这些关键的重要信息 内切酶

The objective is to determine the three-dimensional structures of uridine phosphorylase and thymidine phosphorylase. The pyrimidine phosphorylases may be responsible for the degradation of certain nucleoside analogs of potential chemotherapeutic value. It has been suggested that pyrimidine phosphorylase inhibitors might be useful as chemotherapeutic agents either by enhancing the efficacy of pyrimidine nucleoside analogs or by interfering with pyrimidine base salvage. In addition, the pyrimidine phosphorylases have been utilized in the enzymatic approach to laboratory synthesis of nucleoside analogs. The ultimate goal is to provide precise structural data which can be used in two possible ways. One way is to guide efforts to synthesize new inhibitors of the mammalian enzymes. The second way is to suggest structural modifications which might alter the specificity and stability of the E. coli enzyme leading to a more useful synthetic tool. Such modifications could be performed using standard techniques of genetic engineering. Single-crystal X-ray diffraction methods will be used to determine the crystal structures of uridine phosphorylase and thymidine phosphorylase. Crystals of both enzymes from E. coli have been grown and are suitable for high-resolution crystallagraphic analysis. The structures will be determined using multipe-isomorphous- replacement techniques and refined using intensity data measured with oscillation photography and synchrotron radiation. Once the structures are known, the active sites will be characterized by examining substrate, substrate analog and inhibitor complexes of the enzymes. It is hoped that the high-resolution structures of uridine phosphorylase and thymidine phosphorylase will provide important information towards the understanding of these key enzymes.