Influences of pH and temperature on lysozyme activity in the plasma of Japanese flounder and Japanese char

Abstract

Influences of pH and temperature on lysozyme activity in the plasma from Japanese flounder, Paralichthys olivaceus, and Japanese char, Salverinus leucomaenis, were examined using the turbidimetric assay system. Phosphate buffered solution adjusted at pH 6.1 promoted the highest activity of lysozyme in both fishes. The optimal temperature for the bacteriolytic activity of lysozyme in Japanese flounder and Japanese char was 50°C and 30°C, respectively. The lysozyme activities of both species of fish were heat labile at temperatures higher than 48°C for 30 min, and were stable at lower than 30°C for 48 h. These results may be useful in establishing a simple assay system for lysozyme activities in order to evaluate bio-defense level in both fish.