Lysozymerelated

Lysozyme-related refers to enzymes and protein domains that are evolutionarily related to lysozyme, particularly proteins sharing the lysozyme-like fold or belonging to the same muramidase family. The category includes true lysozymes, such as c-type lysozymes found in many animals, as well as lysozyme-like proteins that retain structural similarity but may have altered or no catalytic activity. In some contexts, "lysozyme-related" also covers distant homologs whose functions have diversified beyond peptidoglycan hydrolysis.

Lysozymes are small globular proteins, commonly around 130 amino acids, and many adopt a packed β-sheet core with a catalytic cleft. The enzymatic mechanism typically uses a pair of catalytic residues to hydrolyze the β-(1,4) glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan. The active site and substrate-binding groove are highly conserved within lysozyme families, though different types exhibit variations in substrate range and pH activity.

Lysozyme is abundant in secretions such as egg white, tears, saliva, and mucus, contributing to innate immune defense by destroying bacterial cell walls, especially Gram-positive bacteria. Lysozyme-related proteins are widespread in animals, plants, and microbes. Some human proteins related to lysozyme (lysozyme-like or LYZL proteins) retain the fold but lack hydrolytic activity, with roles proposed in immune regulation or reproductive tissues. Allergies to egg white are commonly linked to lysozyme.

From a research perspective, lysozyme-related proteins have been central to studies of protein structure, folding, and enzyme mechanisms; lysozyme was among the early proteins whose structure was determined by crystallography. Biotechnological uses include food preservation and potential medical applications, with ongoing work to engineer activity, stability, and spectrum of antimicrobial action. Evolutionarily, gene duplication and divergence have produced a family of related enzymes and non-enzymatic relatives across taxa.