Lysozyme (muramidase) hydrolyses preferentially the β-1,4 glucosidic linkages between N-acetylmuramic acid and N-acetylglucosamine which occur in the mucopeptide cell wall structure of certain microorganisms, such as Micrococcus lysodeikticus.

• Extinction coefficient (E1%): 26,4 (280 nm)
• Isoelectric point (pI): pH 11,0
• Enzyme Commission Number: E.C.3.2.1.17

It hydrolyzes β(1→4) linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrin. Gram-positive cells are quite susceptible to this hydrolysis as their cell walls have a high proportion of peptidoglycan. Gram-negative bacteria are less susceptible due to the presence of an outer membrane and a lower proportion of peptidoglycan.

It has been used for lysing E. coli and Streptomycetes for extraction purposes such as extracting group specific antigen. It would appear that lysozyme may act as a germinative agent of bacterial spores.In humans, lysozyme may be the mediator in the anti-tumor function of macrophages which, it has been shown, secrete the enzyme. There is evidence that cartilage lysozyme has a role in cartilage calcification. Enzyme breaks down the cell walls of bacteria used to prepare spheroplasts.

Unit definition: One unit will cause a decrease in A450 of 0,001 per minute at pH 6,24 and 25 °C using Micrococcus lysodeikticus as substrate.