Characteristic and application of Sciaenops ocellatus serum lysozyme

Serum lysozyme of Sciaenops ocellatus was isolated by the method of(NH4)2SO4 precipitation.Effects of pH and temperature on activity of the lysozyme were examined using the spectrophotometric method.The heat stability of the lysozyme and effect of metal ions on it in vitro as well as influence of the lysozyme on hybrid tilapia were also researched.The results showed that optimal pH and temperature on lysozyme activity was 6.84 and 31 ℃ respectively.The enzyme was heat labile at temperatures above 60 ℃ for 30 min,and stable at below 60 ℃.Cd2+,Pb2+,Ag+ and Mn2+ restrained significantly the lysozyme activities.And Ca2+ and Na+ could activate the lysozyme.Results may be useful in establishing a simple assay system for lysozyme activities in order to evaluate bio-defense level in fish.Additionally,the survival rate of hybrid tilapia was improved by the lysozyme treatment.