Lysozyme (E1105, muramidase) is a naturally occurring antimicrobial enzyme found in hen egg white (HEW), human tears, saliva, and milk. Commercial production involves extraction and purification from egg white by ion-exchange chromatography. This yields a highly active and stable enzyme.
Lysozyme's substrate specificity is the beta-1,4-glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine in bacterial peptidoglycan, selectively lysing Gram-positive bacteria such as Listeria, Clostridium, and Bacillus species. Its activity is enhanced by EDTA and other chelating agents that disrupt the outer membrane of Gram-negative bacteria to expose the inner peptidoglycan layer. It is approved as E1105 in the EU for cheese and wine, and holds GRAS status in the US. It is heat-stable under acidic conditions and active across pH 3–9.