Active Site Modifications of Organophosphorus Hydrolase for Improved Detoxification of Organophosphorus Neurotoxins

Abstract

Amino acid substitutions within the active site of the dimeric metalloenzyme Organophosphorus Hydrolase (OPH) result in a striking enhancement in the hydrolysis of certain chemical warfare agents and their analogues. These changes alter the metal content of the enzyme and we suggest that changes in metal requirements improve the catalytic characteristics by allowing greater structural flexibility and access of larger substrates to the active site. Crystallographic and three-dimensional modeling analyses have suggested that removing steric hindrances in the vicinity of the binding pocket could further enhance the effectiveness of OPH to hydrolyze VX. These studies also suggest that the hydrogen-bonding network supplying support and stability to the active site deserve a critical analysis for further catalytic improvements. The broad substrate specificity and hydrolytic efficiency of OPH and the ability to genetically engineer the enzyme for specific target organophosphate neurotoxins have provided realistic OPHbased technologies for detoxification of these compounds, including enzyme immobilization on various matrices, discriminative detection, and clinical therapy. A series of optimized enzymes for individual substrates can be envisioned that would maximize degradative activity under a particular environmental situation. The capacity for further improvement is remarkable, and the opportunity for a variety of biotechnological applications is quite pronounced.