Lysozyme

Definition

An antimicrobial enzyme and glycoside hydrolase that hydrolyzes (1→4)-β-linkages in bacterial peptidoglycan, degrading cell walls and causing osmotic lysis. Found in arthropod hemolymph, secretions, and gut fluids as a constitutive defense of innate immunity.

Etymology

From Greek lysis (loosening, dissolution) + enzyme

Example

Honey bees (Apis mellifera) produce lysozyme in their hypopharyngeal glands; the enzyme is transferred to larval food and also found in royal jelly, providing antimicrobial protection to developing brood.

Synonyms

• muramidase
• N-acetylmuramide glycanhydrolase

Related Terms

• innate immunity
• Hemolymph
• antimicrobial peptide
• peptidoglycan
• prophenoloxidase
• defensin
• Chitinase

Usage Notes

In arthropods, lysozyme complements inducible defenses such as antimicrobial peptides and the prophenoloxidase cascade. Activity levels vary widely across taxa and tissues; some social insects show exceptionally high concentrations. Not to be confused with lytic enzymes targeting chitin (chitinases), though both act on β-linked polysaccharides.