|-
| align="center" colspan="2" |
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| colspan="2" bgcolor="#dddddd" | Identifiers
|-
| bgcolor="#e7dcc3" | Symbol(s)
| bgcolor="#eeeeee" | [LYZ]
|-
| bgcolor="#e7dcc3" | Entrez
| bgcolor="#eeeeee" | [4069]
|- class="hiddenStructure"
| bgcolor="#e7dcc3" | OMIM
| bgcolor="#eeeeee" | [153450]
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| bgcolor="#e7dcc3" | RefSeq
| bgcolor="#eeeeee" | [NM_000239]
|-
| bgcolor="#e7dcc3" | UniProt
| bgcolor="#eeeeee" | [P61626]
|- class="hiddenStructure"
| bgcolor="#e7dcc3" | PDB
| bgcolor="#eeeeee" | []
|-
| colspan="2" bgcolor="#dddddd" | Other data
|- class="hiddenStructure"
| bgcolor="#e7dcc3" | EC number
| bgcolor="#eeeeee" | [3.2.1.17]
|-
| bgcolor="#e7dcc3" | Locus
| bgcolor="#eeeeee" | Chr. 12[]
|-
|}
Lysozyme is an enzyme (EC [3.2.1.17]), commonly referred to as the "body's own antibiotic" since it kills bacteria. It is abundantly present in a number of secretions, such as tears (except bovine tears). This protein is present in cytoplasmic granules of the polymorphonuclear neutrophils (PMN) (except for bovine neutrophils) and released through the mucosalsecretions (such as tears and saliva). They can also be found in high concentration in egg white.
Most of the bacteria affected by lysozyme are not pathogenic. It could be argued that lysozyme is a primary reason these organisms did not develop pathogenic strains[[Citing sources citation needed]].
Lysozyme serves as an unspecific innate opsonin by binding to the bacterial surface to reduce the negative charge and facilitate phagocytosis of this bacterium before opsonins from the acquired immune systems enter the scene. In other words, a lysosyme makes it easier for white blood cells to eat bacteria.
The enzyme functions by attacking peptidoglycans and hydrolyzing the bond that connects N-acetyl muramic acid with the fourth carbon atom of N-acetylglucosamine. It does this by binding to the peptidoglycan molecules in the binding site within the prominent cleft between it's two domains. This causes the substrate molecule to adopt a strained conformation similar to that of the transition state. The amino acid side chains Glutamic acid 35 and Aspartate 52 have been found to be critical to the activity of this enzyme. Glu 35 acts as a proton donor to the glycosidic bond cleaving the C-O bond in the substrate, whilst Asp52 stabilizes the carbonium ion intermediate until it reacts with a free water molecule, extracting a hydroxl group and freeing a proton that bonds to Glu35, leaving the enzyme unchanged it.
Lysozyme levels in the blood are often increased in sarcoidosis.
Levels are considered raised at 8 mg/l or above.The predictive value for raised ACE level and lysozyme raised level (in combination), for sarcoidosis is up to 83%.
History
Alexander Fleming (1881-1955), who discovered penicillin, described lysozyme in 1922 (Fleming A. On a remarkable bacteriolytic element found in tissues and secretions. Proc Roy Soc Ser B 1922;93:306-17).
Its structure was described by David Chilton Phillips (1924-1999) in 1965 when he got the first 2 angstrom resolution image. This work led Phillips to provide an explanation for how enzymes speed up a chemical reaction in terms of its physical structures.
It was also looked into by Howard Florey (1898-1968)and Ernst B. Chain (1906-1979). Although they never made much progress in this field they developed penicillin, which Fleming had failed to do.
