Biochemical and bacteriological properties of the lysozyme of the clam Tivela stultorum

A lysozyme-like enzyme from the crystalline style of the clam Tivela stulto rum was purified by chromatography of cationic exchange in carboxymethyl ce llulose. The product had a specific activity of 25,407 units per milligram of protein, which represents a purification of 100 times. The specific acti vity observed with this enzyme was almost six times greater than the activi ty observed in the hen egg-white lysozyme under the same conditions. Using the isoelectric focusing technique, a component was observed that indicates an isoelectric point of 7.7 (IEF-PAGE, Phast Gel). A one-dimensional elect rophoresis (SDS-PAGE) revealed an apparent molecular weight of 17,000 dalto ns. The enzyme was optimally active at pH 5.6-5.8. in 0.1 M phosphate-citra te buffer, with maximum activity at a temperature of 40 degrees C, and an i onic strength of 0.1043. At 4 degrees C, the lysozyme presented 26.7% of re mnant activity, and was highly stable at elevated temperatures (90 degrees C) and extreme pHs, from 2.8 to 11.8, with activities above 75%. This enzym e proved to have antimicrobial properties with or without EDTA in the lysis of three bacteria (Streptococcus alfa, Micrococcus lisodeikticus and Esche richia coli), whereas hen egg lysozyme showed lysis in the presence of EDTA on S. alfa and E. coli. The results were also compared against the lysozym e of the scallop Chlamys islandica.