Effects of mercuric ion on the conformation and activity of Penaeus Vannamei beta-N-acetyl-d-glucosaminidase.

Abstract β- N -acetyl- d -glucosaminidase (NAGase, EC.3.2.1.52), a composition of the chitinases, catalyzes the cleavage of N -acetylglucosamine polymers into N -acetylglucosamine. In this paper, the effects of mercuric ion on the activity of NAGase from Penaeus vannamei for the hydrolysis of pNP-NAG have been studied. The results show that HgCl 2 can lead to irreversible inactivation to this enzyme. The inactivation process follows a first-order reaction and the inactivation rate constants have been determined. The relationship between the inactivation rate constants and HgCl 2 concentration has been studied and the result shows that only one molecule of HgCl 2 binds to the enzyme molecule to lead the enzyme lose its activity. Moreover, the conformational changes of the enzyme inactivated by HgCl 2 were studied by following changes in the intrinsic fluorescence emission and ultraviolet absorption spectra.