Lysozymes in the Animal Kingdom

Lysozyme, firstly described by Fleming, in 1922, is a small enzyme able to hydro-lyze the beta-glycosidic linkage between N-acetylmuramic acid and N-acetyl glu-cosamine 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 ani-mals. Three major different types of lysozymes have been identified, differing in amino acids sequences, biochemical and enzymatic properties, and designated as C-type (chicken or conventional type), G-type (goose-type) and I-type (inverte-brate type) lysozyme. 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 defence of these organ-isms against bacterial infections. Apart from the antimicrobial action, lysozymes have many other functions including immune-modulation, immune-stimulation, and anti-cancer action.