Comparative study on characteristics of lysozymes from the hemolymph of three lepidopteran larvae, Galleria mellonella, Bombyx mori, Agrius convolvuli

Lysozymes were purified from the hemolymph of three immunized Lepidopteran larvae, Galleria mellonella, Bombyx mori, Agrius convolvuli to compare their physico-chemical properties and antibacterial activities with those of chicken lysozyme. Four lysozymes including the one from chicken had similar molecular masses and chromatographic behavior on reverse phase-high pressure liquid chromatography. Western blotting analysis using an antibody raised against G. mellonella revealed that lysozyme cross-reacted with two other insect lysozymes but not with commercial chicken lysozyme. Antibacterial activities of lysozymes were measured in two types of tests: radial diffusion assay and colony count assay. Our antibacterial tests revealed that all lysozymes have strong activities against Gram-positive bacteria and three insect lysozymes still retain a little potency against Gram-negative bacteria, while chicken lysozyme has no activity against Gram-negative bacteria. Taken together, we conclude three Lepidopteran lysozymes have a common distinct structure and have an antibacterial activity, which is absent in chicken lysozyme, against Gram-negative bacteria. (C) 2002 Elsevier Science Ltd. All rights reserved.