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Lysozyme

[EC3.2.1.17; 1,4-beta-N-acetylmuramidase C] Two antimicrobial peptides are released from chicken egg white lysozyme after peptic digestion and subsequent tryptic digestion. The peptide corresponding to amino acid residues 98-108 (Lysozyme 98-108; EGLHNYR) inhibits Escherichia coli K-12. The peptide corresponding to amino acid residues 15-21 (Lysozyme 15-21; His-Gly-Leu-Asp-Asn-Tyr-Arg) inhibits S. aureus (Mine et al, 2004). For lysozyme-like proteins see: LLP.

Ibrahim et al (2005) have reported that peptides corresponding to residues 1-38 (Lysozyme 1-38), 18-38 (Lysozyme 18-38), and 39-56 (Lysozyme 39-56) of lysozyme C, which can be generated by pepsin cleavage in the stomach of newborns, are antimicrobial peptides. These peptides may play a role in in the mucosal defense systems. Their lethal effect is due to membrane permeabilization and inhibition of redox-driven bacterial respiration. Ibraham (1998) has discussed the relationship between Lysozyme structure and antimicrobial action, which is independent of its catalytic function. Since partially unfolded Lysozyme exerts broad spectrum antimicrobial action in vitro against Gram-negative and Gram-positive bacteria independent of its catalytic activity, naturally-occurring conformational transition of Lysozyme at physiological temperatures may be a biologically relevant event to switch from enzymatic to antimicrobial specificity.

Pellegrini et al (1997) have identified the pentadecapeptide IVSDGNGMNAWVAWR (amino acids 98-112 (Lysozyme 98-112) of chicken egg white Lysozyme), which can be obtained by digestion of lysozyme with clostripain. This peptide has antimicrobial activity against Serratia marcescens, Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus lentus, but is without muramidase activity. This internal peptide is part of a helix-loop-helix domain (residues 87-114 of hen Lysozyme). Ibraihim et al (2001) have reported that the full HLH domains of chicken and human Lysozyme possess potent microbicidal activity against both Gram-positive and Gram-negative bacteria and the fungus Candida albicans.

Lysozyme has been shown also to possess IPSF [Immunoglobulin production stimulating factor] activity and stimulates IgM production by the human-human hybridoma line, HB4C5, and by human peripheral blood lymphocytes.

For other proteins/peptides with antimicrobial activities and/or functions in innate immunity see also the Innate immunity defense peptides Dictionary section of this encyclopedia.

LAST MODIFIED: February 2008

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