STRUCTURAL STUDIES OF ANTITUMOR AMIDOHYDROLASES

门冬酰胺酶疗法通过使肿瘤细胞挨饿， 肿瘤细胞所需的一种营养物质--天冬酰胺。 急诊大肠杆菌酶是 用于治疗急性淋巴细胞白血病。 几 天冬酰胺酶-天冬酰胺酶对天冬酰胺酶抗性肿瘤有活性， 并且来自假单胞菌7A的酶已经显示出对抗 各种腹水和小鼠实体瘤。 我们建议用X光 衍射技术，以确定晶体结构的 假单胞菌7A和产氨不动杆菌 天冬酰胺酶-天冬酰胺酶和产琥珀酸弧菌天冬酰胺酶， 分辨率为2-2.5 Omicron。 这些酶是四聚体， 分子量约为14万道尔顿。 一张6欧微米分辨率的 利用III型晶体获得不动杆菌酶， 每个不对称单元含有一个亚基。 Patterson旋转方法 用于确定假单胞菌的对称性和方向 四聚体 合成了几种重原子化合物， 提出了精氨酸酶-天冬酰胺酶的特异性标记，这将 便于使用多个同晶置换和异常 散射方法 分子置换技术也将被使用， 特别是对弧菌天冬酰胺酶。 酶的结构将是 比较以获得催化机制的详细图像， 结构的活性位点，并确定之间的关系 分子结构和抗肿瘤活性。 此外，初步 一种新的吲哚基-3-烷烃α-羟化酶的晶体学研究 将进行假单胞菌XA。

Asparaginase therapy selectively inhibits certain cancers by starving the tumor cells of a required nutrient - asparagine. The E. coli enzyme is used in the treatment of acute lymphoblastic leukemia. Several glutaminase-asparaginases are active against asparaginase-resistant tumors, and an enzyme from Pseudomonas 7A has been shown to be active against a variety of ascites and solid tumors in mice. We propose to use X-ray diffraction techniques to determine the crystal structures of the Pseudomonas 7A and Acinetobacter glutaminasificans glutaminase-asparaginases, and of a Vibrio succinogenes asparaginase, at resolutions of 2-2.5 Omicron. The enzymes are tetramers with molecular weights of about 140,000 daltons. A 6 Omicron resolution map of the Acinetobacter enzyme has been obtained utilizing form III crystals, which contain one subunit per asymmetric unit. Patterson rotation methods have been used to determine the symmetry and orientation of the Pseudomonas tetramer. The synthesis of several heavy atom containing compounds for specific labeling of the glutaminase-asparaginases is proposed, which will facilitate the use of multiple isomorphous replacement and anomalous scattering methods. Molecular replacement techniques also will be used, especially for the Vibrio asparaginase. The enzyme structures will be compared to obtain a detailed picture of the catalytic mechanism and structure of the active sites, and to determine the relationships between molecular structure and antitumor activity. In addition, preliminary crystallographic studies of a novel indolyl-3-alkane Alpha-hydroxylase from Pseudomonas XA will be carried out.