Studies of the lysozyme of Mytilus edulis L

Mytilus edulis lysozyme responded differently from hen egg-white (HEW) lysozyme to sodium chloride when assayed by an agar-diffusion (lysoplate) technique with Micrococcus luteus as substrate. However at 1% (w/v) NaCl both enzymes gave similar dose response curves and this concentration was used in all lysoplate assays. The distribution of lysozyme in Mytilus edulis and other bivalves was investigated. In Mytilus the hipest concentrations were found in structures associated with digestion, particularly in the style and digestive gland. Similar distributions were found in Modiolus modiolus, Chlamys opercularis and Tellina tenuis. However, in Mya arenaria, highest concentrations were found in gill and digestive gland which may reflect differences in the choice of food particle if lysozyme is related to the proportion of bacteria utilized from the food. Lysozyme was purified from crystalline styles of Mytilus edulis by chromatography on Amberlite CG-50 carboxymethyl cellulose. The product was 90% pure, with a specific activity of 16,200 enzyme units per mg of protein, representing a 216-fold purification from crystalline style and purification compared to homogenates of whole animals (less shells). Collagenase and beta-glucuronidase activities, which were found in style homogenates were not detected in purified lysozyme. The enzyme satisfied Salton's criteria for lysozyme, lysing bacterial cells and reducing the turbidity of cell wall suspensions with the liberation of reducing groups and an amino sugar complex. The enzyme cleaved the beta1-4 glycosidic linkage between N-acetylmuramic acid and N-acetylglucosamine in the bacterial cell wall and thus was a mucopeptide N-acetylmuramylhydrolase (E.C.3.2.1.17). By sodium dodecyl sulphate polyacrylamide gel electrophoresis, the molecular weight was approximately 18,000 daltons and on isoelectric focusing the isoelectric point was 9.2. On polyacrylamide gel electrophoresis in acid gels Mytilus lysozyme migrated more slowly than HEW lysozyme. Both Mytilus and HEW lysozymes were eluted from Bio-Gel P-60 later than expected from their molecular weights. Also, there was a low recovery of the applied Mytilus lysozyme, possihly due to electrostatic interaction with the gel matrix. Purified Mytilus lysozyme was heat stable in the presence of gelatin and sodium chloride hut was inactivated at room temperature in solution in distilled water. At 10