The Energetics of Enzyme Catalysis

这项工作旨在更深入地理解酶催化的本质。将对两组酶进行研究。首先，对氨基酸消旋酶的作用机理进行了研究，重点介绍了谷氨酸消旋酶和二氨基戊二酸消旋酶的作用机理。这些酶中的每一种都催化x-氨基酸中心的外消旋，而不需要或不涉及磷酸吡哆醛。这些酶将被分离和鉴定，并将通过同位素交换、同位素示踪和微扰实验来探索其反应的能量学。第二组酶是水合酶，这里的主要目标将是确定反应是以协调的方式还是以逐步的方式进行。将使用双同位素分馏试验，并将评估一项新的方案，该方案有可能将这一方法扩展到以前不合适的系统。进行反立体化学的水合作用将与遵循SYN途径的水化作用进行比较。总之，提出的研究将提供关于这些非常有效的反应的密切机制细节的信息。酶是非常有效的催化剂，它能以即使是最好的人造催化组件所罕见的速度来调节特定的化学转化。如果我们能够追踪催化效率的发展，我们应该能够更好地理解我们今天所发现的酶催化的本质。诺尔斯博士对简单系统的尖锐抨击无疑正在取得进展。

This work is aimed at a deeper understanding of the nature of enzyme catalysis. Two groups of enzymes will be studied. First, the mechanism of amino acid racemases will be investigated, with particular focus on glutamate racemase and diaminopimelate empimerase. Each of these enzymes catalyzes the racemization of an x-amino acid center without the need for or involvement of pyridoxal phosphate. The enzymes will be isolated and characterized, and the energetics of their reactions will be explored by the use of isotope exchange, isotope tracer, and perturbation experiments. The second group of enzymes are the hydratases, and the primary goal here will be to determine whether the reactions proceed in a concerted or stepwise fashion. The double isotope fractionation test will be used, and a new protocol will be evaluated that has the potential for extending this methodology to previously inappropriate systems. Hydrations that proceed with anti stereochemistry will be compared with those that follow a syn pathway. Together, the studies proposed will provide information about the intimate mechanistic details of these very efficient reactions. Enzymes are formidably efficient catalysts that mediate specific chemical transformations at rates rarely approached by even the best of man-made catalytic assemblies. If we could trace the development of catalytic efficiency we should be better able to understand the nature of enzyme catalysis as we find it today. Dr. Knowles is certainly making headway with his incisive attack on simple systems.