3-D STRUCTURES OF URIDINE & THYMIDINE PHOSPHORYLASES

我们的目标是确定其三维结构 尿苷磷酸化酶和胸苷磷酸化酶。这个 嘧啶磷酸化酶可能是降解的原因。 潜在化疗药物的某些核苷类似物 价值。已有研究表明，嘧啶磷酸化酶 抑制剂可能是有用的化疗药物，通过以下方式 增强嘧啶核苷类似物的疗效或通过 干扰嘧啶碱基打捞。此外， 嘧啶磷酸化酶已在酶促反应中得到应用。 核苷类似物的实验室合成方法。这个 最终目标是提供精确的结构数据，可以 有两种可能的用法。一种方法是引导努力 合成新的哺乳动物酶抑制剂。第二 方法是建议结构修改，这可能会改变 大肠杆菌酶的特异性和稳定性导致更多的 有用的合成工具。可以执行这样的修改 使用标准的基因工程技术。单晶 将使用X射线衍射法来确定晶体 尿苷磷酸化酶和胸苷磷酸化酶的结构。 来自大肠杆菌的这两种酶的晶体已经培养出来，并正在 适用于高分辨率的晶相分析。这个 结构将使用多重同构-确定 替换技术和改进的使用强度测量数据 具有振荡照相和同步辐射。一旦 结构是已知的，活性中心的特征是 检测底物、底物类似物和抑制剂复合体 这些酶。人们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 有助于理解这些关键信息的重要信息 酵素。

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.