Inhibition kinetics of hydrogen peroxide on β-N-acetyl-d-glucosaminidase from prawn (Penaeus vannamei)

Abstract

The effects of hydrogen peroxide (H 2 O 2 ) on prawn NAGase activity for the hydrolysis of pNP-b-D-GlcNAc have been studied. The results show that H 2 O 2 can reversible inhibit the enzyme (IC 50°0 .85 M) and the inhibition is of a mixed type. The kinetics show that k þ0 is much larger than k 0 þ0 ; indicating the free enzyme is more susceptible than the enzyme-substrate complex in the H 2 O 2 solution. It is suggested that the presence of the substrate offers marked protection against inhibition by H 2 O 2 . Changes of activity and conformation of the enzyme in different concentrations of H 2 O 2 have been compared by measuring the fluorescence spectra and residual activity and show that the change of conformation is more rapidly than that of the residual activity, which implies that the whole conformation of the enzyme changes more rapidly than the conformation of the active centre of the enzyme in the H 2 O 2 solution.

Inhibitory kinetics of β‐N‐acetyl‐D‐glucosaminidase from prawn (Litopenaeus vannamei) by zinc ion

“…The progress‐of‐substrate reaction method previously described by Tsou (18) and Xie et al (19) was used to study the inhibition kinetics of Zn 2+ on prawn NAGase. The time course of the hydrolysis of the substrate in the presence of different Zn 2+ concentrations was shown in Fig.…”

“…The progress‐of‐substrate reaction method previously described by Tsou (18) and Xie et al (19) was applied to the study of the inhibition kinetics of prawn NAGase by Zn 2+ . In this method, 10 μL of enzyme was added to 2.0 mL assay system containing different concentrations of substrate in 0.1 M NaAc‐HAc buffer (pH 5.8) with different concentrations of Zn 2+ .…”

“…The equilibrium constant was determined to be 11.92 mM using a standard Lineweaver–Burk plot. Applying the theory of the substrate reaction previously described by Tsou (18) and Xie et al (19), the inhibition kinetics of prawn NAGase by Zn 2+ at low concentrations was studied. The inhibitory equilibrium constant was determined to be 11.96 mM, which was accordant with that obtained from a standard Lineweaver–Burk plot.…”

“…In our investigation, we found that L. vannamei NAGase activity could be affected by Zn 2+ , and the inhibition of the enzyme by Zn 2+ was shown to be reversible. Therefore, the aim of this article is to concentrate on the kinetics of inhibition of the enzyme by Zn 2+ using the substrate reaction kinetics method described by Tsou (18) and Xie et al (19), and to similarly measure the rate constants of reversible inactivation and reactivation.…”

Inhibitory kinetics of bromacetic acid on β-N-acetyl-d-glucosaminidase from prawn (Penaeus vannamei)

“…NCIM 5120. In our previous studies, we reported the purification and some enzymatic characterization of NAGase from prawn (Penaeus vannamei) [14], and the inactivation kinetics of mercuric ion [15], hydrogen peroxide [16], formaldehyde [17] and dioxane [18] on the enzyme has been well studied, respectively. Systematical studies of NAGase from P. vannamei are currently taking place in our laboratory.…”