Comparison of the Properties of NAGase from the Hepatopancreas of Prawn(Lifopenaeus vannamei) in Different Growth Stages

The β-N-acetyl-D-glucosaminidase(NAGase,EC 3.2.1.52) from L.vannamei is tightly related to periodical molting and growth of the prawn.We studied the variations of activity and basic properties of NAGase from the hepatopancreas of the prawn in different growth stages.The results showed that the enzyme activities of the prawn from different growth stages are variational.The enzyme activity of the larvae is 40 U per mg of protein.As the larvae growed,the activity decreased rapidly.The enzyme activity in the 6 week-period feeding decreased to the lowest point of 18 U per mg of protein.Then the enzyme activity increased rapidly.The enzyme activities in the mature prawn reached a maximum of 58 U per mg of protein.The optimum pH of the enzyme in different growth stages were between 5.5 and 6.0.The optimum temperature changed from 34℃ to 37℃.The kinetic parameters,active energy and the sensitivities to Cu~(2+),Zn~(2+) and Hg~(2+) of the enzyme in different growth stages were tested and compared.