Studies on the Mechanism and Control of Enzyme Action

来自大肠杆菌的腺苷琥珀酸合成酶（Adenylosuccinate synthetase）是在从头嘌呤核苷酸生物合成途径中将IMP转化为AMP的第一步，其结构作为未连接的酶并与各种底物和底物类似物络合，现在是可用的。在拟议的资助期间，PI将根据晶体结构制备和研究AMPSase突变形式的特性，试图在分子水平上深入了解酶的催化和调节机制。那些似乎感兴趣的AMPSase突变形式将在可能的地方结晶并进行结构分析。AMPSase的调控模式尚不清楚；然而，亚基结合的状态可能在AMPSase活性的调节中发挥作用，这种可能性将使用动力学和物理技术进行研究。研究发现，两种不同的无活性AMPSase突变体的混合可导致活性异二聚体的形成。这一发现背后的物理基础将被调查。AMPSase合成酶是一种在所有生物体中起着至关重要作用的酶。它催化嘌呤核酸生物合成的第一步，嘌呤核酸继续形成DNA和RNA，以及其他在代谢调节中重要的细胞核苷酸。了解这种酶的功能也有助于设计化疗药物。＊＊＊

9603595 Fromm The structure of Adenylosuccinate synthetase from E. coli, the first committed step in the conversion of IMP to AMP in the de novo purine nucleotide biosynthetic pathway, as the unligated enzyme and complexed, with a variety of substrates and substrate analogs, is now available. During the proposed grant period the PI will prepare and study the properties of mutant forms of AMPSase, based on the crystal structure, in an attempt to gain insight into the enzyme's catalytic and regulatory mechanisms at the molecular level. Those mutant forms of AMPSase that appear to be of interest will be crystallized where possible and subjected to structural analysis. The mode of AMPSase regulation is not known; however, the state of subunit association may play a role in the regulation of AMPSase activity and this possibility will be investigated using both kinetic and physical techniques. It was found that mixing of two different inactive mutant forms of AMPSase can lead to the formation of active heterodimers. The physical basis behind this finding will be investigated. *** AMPSase synthetase is an enzyme that plays a crucial role in all living organisms. It catalyzes the first committed step in the biosynthesis of purine nucleic acids, which go on to form DNA and RNA, along with other cellular nucleotides of importance in regulation of metabolism. Understanding how this enzyme functions can also have potential for the design of chemotherapeutic agents. ***