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

Abstract

The effects of hydrogen peroxide (H₂O₂) on prawn NAGase activity for the hydrolysis of pNP-β-D-GlcNAc have been studied. The results show that H₂O₂ can reversible inhibit the enzyme (IC₅₀ ≏ 0.85 M) and the inhibition is of a mixed type. The kinetics show that k₊₀ is much larger than indicating the free enzyme is more susceptible than the enzyme-substrate complex in the H₂O₂ solution. It is suggested that the presence of the substrate offers marked protection against inhibition by H₂O₂. Changes of activity and conformation of the enzyme in different concentrations of H₂O₂ 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 H₂O₂ solution.

Keywords::

• Penaeus vannamei
• β-N-acetyl-D-glucosaminidase
• inhibition kinetics
• hydrogen peroxide
• conformation
• activity

Acknowledgements

The present investigation was supported by grant 2004J054 of the Scientific Technology Innovation Fund for the Young Scholar of Fujian Province.