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Inhibitory kinetics of β ‐ N ‐acetyl‐ D ‐glucosaminidase from prawn ( Litopenaeus vannamei ) by zinc ion
Author(s) -
Xie XiaoLan,
Huang QianSheng,
Gong Min,
Du Juan,
Yang Yi,
Chen QingXi
Publication year - 2009
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1002/iub.140
Subject(s) - prawn , chemistry , zinc , enzyme , kinetics , reaction rate constant , litopenaeus , substrate (aquarium) , absorbance , cysteine , enzyme assay , histidine , biochemistry , nuclear chemistry , chromatography , shrimp , biology , fishery , ecology , physics , organic chemistry , quantum mechanics
Prawn ( Litopenaeus vannamei ) β‐ N ‐acetyl‐ D ‐glucosaminidase (NAGase, EC 3.2.1.52) is involved in the digestion and molting processes. Zinc is one of the most important metals often found in the pollutant. In this article, the effects of Zn 2+ on prawn NAGase activity for the hydrolysis of pNP‐NAG have been investigated. The results showed that Zn 2+ could reversibly and noncompetitively inhibit the enzyme activity at appropriate concentrations and its IC 50 value was estimated to be 6.00 ± 0.25 mM. The inhibition model was set up, and the inhibition kinetics of the enzyme by Zn 2+ has been studied using the kinetic method of the substrate reaction. The inhibition constant was determined to be 11.96 mM and the microscopic rate constants were also determined for inactivation and reactivation. The rate constant of the inactivation ( k +0 ) is much larger than that of the reactivation ( k −0 ). Therefore, when the Zn 2+ concentration is sufficiently large, the enzyme is completely inactivated. On increasing the concentration of Zn 2+ , the fluorescence emission peak and the UV absorbance peak are not position shifted, but the intensity decreased, indicating that the conformation of Zn 2+ ‐bound inactive NAGase is stable and different from that of native NAGase. We presumed that Zn 2+ made changes in the activity and conformation of prawn NAGase by binding with the histidine or cysteine residues of the enzyme. © 2008 IUBMB IUBMB Life, 61(2): 163–170, 2009