Lysozyme (E1105, muramidase) là enzyme kháng khuẩn tự nhiên có trong lòng trắng trứng gà (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.