N-Acetyl-β-D-glucosaminidase（NAGase, EC 3.2.1.52）, which catalyzes the cleavage of N-acetylgluco- samine polymers, plays important roles in the molting, digestion of chitinous foods in green crab. In the study, the...N-Acetyl-β-D-glucosaminidase（NAGase, EC 3.2.1.52）, which catalyzes the cleavage of N-acetylgluco- samine polymers, plays important roles in the molting, digestion of chitinous foods in green crab. In the study, the efforts of urea on the activity of NAGase purified from the viscera of green crab（Scylla serrata） have been studied. The results show that appropriate concentrations of urea can lead to reversible inactivation of the enzyme, and the value of the inhibitor concentration leading to 50% of enzyme activity lost（IC50） is estimated to be 0.63 mol/L. The inactivation kinetics has been studied via the kinetic method of the substrate reaction. The rate constants of inactivation have been determined. The value of k＋0 is larger than that of k′＋0, indicating the free enzyme molecule is more fragile than the enzyme-substrate complex in urea solution. It is suggested that the presence of the substrate offers the marked protection of this enzyme against inactivation by urea.展开更多
基金Supported by the National Natural Science Foundation of China(No.40576066)the Science and Technology Foundation of Xiamen,China(No.3502Z20081143)
文摘N-Acetyl-β-D-glucosaminidase（NAGase, EC 3.2.1.52）, which catalyzes the cleavage of N-acetylgluco- samine polymers, plays important roles in the molting, digestion of chitinous foods in green crab. In the study, the efforts of urea on the activity of NAGase purified from the viscera of green crab（Scylla serrata） have been studied. The results show that appropriate concentrations of urea can lead to reversible inactivation of the enzyme, and the value of the inhibitor concentration leading to 50% of enzyme activity lost（IC50） is estimated to be 0.63 mol/L. The inactivation kinetics has been studied via the kinetic method of the substrate reaction. The rate constants of inactivation have been determined. The value of k＋0 is larger than that of k′＋0, indicating the free enzyme molecule is more fragile than the enzyme-substrate complex in urea solution. It is suggested that the presence of the substrate offers the marked protection of this enzyme against inactivation by urea.
