Denaturation/Renaturation of Organophosphorus Acid Anhydrolase (OPAA) Using Guanidinium Hydrochloride and Urea

The understanding of how protein unfolds/refolds is a key to the development of any protein/enzyme based detection system. Using organophosphorus acid anhydrolase (OPAA) as the model protein, a guanidinium hydrochloride and urea denaturation/renaturation study was conducted and measured both optically and enzymatically. As expected, the highly autofluorescent tryptophan moiety (Ex. 280/Em. 340nm) decreased in intensity and red-shifted as denaturant concentration was increased and vice versa upon renaturation; thereby indicating conformational changes. Similar results were obtained with circular dichroism as the peak representing the alpha-helix conformation decreased as denaturant concentration was increased. Likewise, OPAA activity decreased with increasing urea concentration. However with guanidinium hydrochloride little to no enzymatic activity upon denaturation or renaturation was detected. With the fundamental understanding of protein chain folding, one can design nanoencapsulated enzyme systems for detection and decontamination of chemical warfare agents.