Has antibacterial activity against the Gram-positive bacteria L.garvieae, M.luteus and Enterococcus sp., and the Gram-negative bacteria E.coli and V.vulnificus. Weak antibacterial activity against the Gram-negative bacterium A.hydrophila. No antibacterial activity detected against the Gram-positive bacterium S.iniae or against the Gram-negative bacterium E.ictaluri. Shows some chitinase activity but no isopeptidase activity. Hydrolysis of (1->4)-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrins. Optimum pH is 5.5-6.0. Activity increases as temperature increases from 0 to 45 degrees Celsius and decreases markedly at temperatures greater than 55 degrees Celsius. Hemolymph, labial palps, non-vesiculated cells of mantle connective tissue, cells of interlamellar junctions and epithelia surrounding the water tubes of the gills. Belongs to the glycosyl hydrolase 22 family. Type-I lysozyme subfamily.