Lysozyme is a compact, globular protein found abundantly in the specific granules of human polymorphonuclear leukocytes, as well as in various secretions such as tears, saliva, and egg white. Its primary function is to provide innate immune defense by hydrolyzing the β-1,4 glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine residues in the peptidoglycan layer of bacterial cell walls, particularly targeting Gram-positive bacteria. Lysozyme’s active site, located in a deep groove on its surface, binds to bacterial polysaccharide chains, facilitating their cleavage and leading to bacterial lysis and death.

Beyond its antibacterial role, lysozyme exhibits antifungal and antiviral activities and modulates immune responses by influencing cytokine production and inflammation.