Lysozyme is an enzyme that hydrolyzes the glycosidic bonds of peptidoglycan, and thereby causes bacterial cell lysis. This enzyme constitutively occurs in low levels in hemolymph of most insects. Lysozyme is rapidly induced immediately upon bacterial infection. It is not too surprizing, then, to learn that representatives of various insect orders produce different antibactieral proteins. The attacins and cecropins are known mostly from lepidopterans, although they have been detected in other insects and even in intestine of pigs.
Honeybees produce another family of such proteins that are known as apidaecins.
These are small peptides, molecular weight about 2100. Apidaecins do not appear to disturb bacterial membranes, and it is not yet clear how they do work. It is speculated that these are bacteriostatic, rather than bacteriocidal, proteins. Royalisin is another antibacterial peptide is found in the royal jelly of honeybees. This is also an amphipathic protein, and its mode of action may be similar to cecropins.