Lysozymes in the Animal Kingdom

Lysozyme, first described by Fleming in 1922, is a small enzyme able to hydrolyze the beta-glycosidic linkage between N-acetylmuramic acid and N-acetyl glucosamine in the peptidoglycan of bacterial cell walls and to bind polymers of N-acetyl glucosamine. It is widely distributed in the animal kingdom and is able to destroy most of the organisms pathogenic either against humans or lower animals. Three major different types of lysozymes have been identified, differing in amino acid sequences, biochemical and enzymatic properties, and designated as C-type (chicken or conventional type), G-type (goose-type), and I-type (invertebrate type) lysozymes. Other minor types of lysozymes can also be identified in plants, bacteria, phages, and fungi. Lysozymes are an important part of human and animal immune systems and play a key role in the defense of these organisms against bacterial infections. Apart from the antimicrobial action, lysozymes have many other functions including immune modulation, immune stimulation, and anticancer action.