High Resolution X-ray Study of Cofactor Dependent Enzyme and Biocatalyst Design

用X射线晶体学方法测定了谷氨酰胺转酰胺酶、变构CTP合成酶、PLP依赖酶和FAD依赖酶等天然复合催化剂的高分辨结构。通过对底物识别、诱导匹配和反应机理的分析，了解了使这些酶能够作为生物催化剂的分子设计。天然生物催化剂的三维结构与活性部位设计。（1）咪唑甘油磷酸合成酶。氨转移机制通过分子通道连接氨基转移酶和合成酶的网站已被提出。（2）CTP合成酶。氨隧道，变构GTP激活，ATP和UTP依赖的构象变化诱导的酶激活的机制进行了研究。（3）精氨琥珀酸合成酶。通过对底物识别机理的研究和伪时间分辨X射线分析，阐明了底物识别的机理。 ...更多信息 反应的化学反应。(4)奎诺血红素蛋白胺脱氢酶。一个新的奎宁辅因子和非常不寻常的硫醚交叉桥已被确定。PLP依赖性酶的三维结构。（1）组氨醇-磷酸氨基转移酶。分析了双底物识别的活性位点设计。（2）支链氨基酸氨基转移酶。阐明了双底物识别和反应机理。（3）苏氨酸合成酶。预期催化的反应通过PLP依赖性酶所利用的所有中间体进行。提出了反应的立体化学。（4）谷氨酰胺/苦氨酸氨基转移酶。在哺乳动物中，该酶参与CNS事件。研究了基底识别和诱导拟合现象. FAD依赖性酶的三维结构。（1）中链酰基辅酶A氧化酶。与同系物（酰基辅酶A脱氢酶）的结构比较的基础上，氧化酶的分子设计进行了分析。（2）中链酰基辅酶A脱氢酶作为过渡态类似物。根据配合物的X-射线结构和分子轨道计算，研究了反应的过渡态。少

High-resolution Structures of natural composite catalysts such as glutamine amidotransferase, and allosteric CTP synthetase, PLP-dependent enzymes, and FAD-dependent enzymes have been determined by X-ray crystallographic methods. The substrate recognition, induced fit, and reaction mechanism have been analyzed to understand the molecular design which enables these enzymes to act as biocatalysts.1. Three-dimensional structures of natural biocatalysts and active-site designs. (1)Imidazole glycerol phosphate synthetase. The ammonia transfer mechanism through a molecular channel linking glutaminase and synthase sites has been proposed. (2)CTP (cytidine 5'-triphosphate) synthetase. The mechanism for ammonia tunneling, allosteric GTP activation, and enzyme activation induced by ATP and UTP-dependent conformational change has been examined. (3)Argininosuccinate synthetase. The substrate recognition mechanism and pseudo time-resolved X-ray analysis has been performed in order to clarify the st … More ereochemistry of the reaction. (4) Quinohemoprotein aminedehydrogenase. A novel quinine cofactor and highly unusual thioether cross-bridges have been identified.2. Three-dimensional structures of PLP-dependent enzymes. (1)Histidinol-phosphate aminotransferase. The active-site design for double substrate recognition has been analyzed. (2)Branched-chain amino acid aminotransferase. The double substrate recognition and reaction mechanism have been elucidated. (3)Threonine synthase. The reaction catalyzed is expected to proceed through all the intermediates utilized by PLP-dependent enzymes. Stereochemistry of the reaction has been proposed. (4)Glutamine/kunerenine aminotransferase. In mammals, the enzyme is involved in CNS events. The substrate recognition and induced fit phenomena have been examined.3. Three dimensional structures of FAD-dependent enzymes. (1)Medium-chain acyl-CoA oxidase. On the basis of structural comparison with the homologue (acyl-coA dehydrogenase), the molecular design of the oxidase has been analyzed. (2)Medium-chain acyl-CoA dehydrogenase as the transition state analogue. The transition state of the reaction has been examined based on the X-ray structure and MO calculation of the complex. Less