Rational design of human paraoxonase to design enhanced catalytic efficiency

U.S. Army Medical Research Inst Chem Def, Aberdeen Proving Ground MD

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Abstract

The toxic effects observed during episodes of chemical nerve agent exposure are primarily the result of the[unreadable] irreversible inhibition of acetylcholinesterases (AChEs). These enzymes play an important role in the[unreadable] regulation of neural signalling throughout the body. Inhibition of AChEs invariably leads to the deregulation[unreadable] of post-synaptic targets (i.e. heart, lungs, etc) and may lead to death. Human paraoxonase (HuPONI) is a[unreadable] serum protein capable of hydrolyzing these deadly toxins, however, its catalytic capacity must be optimized[unreadable] before it can be successfully used as a viable antidote to treat nerve agent poisoning. The objective of this[unreadable] application is the design and synthesis of HuPONI variants capable of detoxifying nerve agents before they[unreadable] can reach their physiological targets and exert a lethal effect. To do this we will define amino acid residues[unreadable] (in or near the active site of the enzyme) that may play a role in the breakdown of chemical nerve agents. By[unreadable] using rational design we will generate variants of the native HuPONI enzyme and test their capacity to[unreadable] catalyltically hydrolyze nerve agents such as tabun (GA), sarin (GB), soman, (GD), and VX. This will be[unreadable] accomplished by the examination of the alteration in the affinity of HuPONI for the nerve agents and / or[unreadable] actual enhancement of its machinery to break down these toxins. Aims 1 and 2 will address the most[unreadable] successful approach to functional expression of various mutant proteins. Based on the results obtained, aims[unreadable] 3 and 4 seek to refine our knowledge of the substrate specificity of this enzyme. We estimate that if the[unreadable] catalytic potential of HuPONI can be enhanced by at least 10-fold, it truly could be a viable anti-nerve agent[unreadable] drug.