Lysozyme Identifiers EC number 3.2.1.17 CAS number 9001-63-2 IntEnz IntEnz view BRENDA BRENDA entry ExPASy NiceZyme view KEGG KEGG entry MetaCyc metabolic pathway PRIAM profile PDB structures Gene Ontology AmiGO / EGO Search PMC articles PubMed articles

edit Lysozyme PDB rendering based on 132l. Available structures 133l, 134l, 1b5u, 1b5v, 1b5w, 1b5x, 1b5y, 1b5z, 1b7l, 1b7m, 1b7n, 1b7o, 1b7p, 1b7q, 1b7r, 1b7s, 1bb3, 1bb4, 1bb5, 1c43, 1c45, 1c46, 1c7p, 1cj6, 1cj7, 1cj8, 1cj9, 1ckc, 1ckd, 1ckf, 1ckg, 1ckh, 1d6p, 1d6q, 1di3, 1di4, 1di5, 1eq4, 1eq5, 1eqe, 1gay, 1gaz, 1gb0, 1gb2, 1gb3, 1gb5, 1gb6, 1gb7, 1gb8, 1gb9, 1gbo, 1gbw, 1gbx, 1gby, 1gbz, 1gdw, 1gdx, 1ge0, 1ge1, 1ge2, 1ge3, 1ge4, 1gev, 1gez, 1gf0, 1gf3, 1gf4, 1gf5, 1gf6, 1gf7, 1gf8, 1gf9, 1gfa, 1gfe, 1gfg, 1gfh, 1gfj, 1gfk, 1gfr, 1gft, 1gfu, 1gfv, 1hnl, 1i1z, 1i20, 1i22, 1inu, 1ioc, 1ip1, 1ip2, 1ip3, 1ip4, 1ip5, 1ip6, 1ip7, 1iwt, 1iwu, 1iwv, 1iww, 1iwx, 1iwy, 1iwz, 1ix0, 1iy3, 1iy4, 1jka, 1jkb, 1jkc, 1jkd, 1jsf, 1jwr, 1laa, 1lhh, 1lhi, 1lhj, 1lhk, 1lhl, 1lhm, 1lmt, 1loz, 1lyy, 1lz1, 1lz4, 1lz5, 1lz6, 1lzr, 1lzs, 1op9, 1oua, 1oub, 1ouc, 1oud, 1oue, 1ouf, 1oug, 1ouh, 1oui, 1ouj, 1qsw, 1re2, 1rem, 1rex, 1rey, 1rez, 1tay, 1tby, 1tcy, 1tdy, 1ubz, 1w08, 1wqm, 1wqn, 1wqo, 1wqp, 1wqq, 1wqr, 1yam, 1yan, 1yao, 1yap, 1yaq, 207l, 208l, 2bqa, 2bqb, 2bqc, 2bqd, 2bqe, 2bqf, 2bqg, 2bqh, 2bqi, 2bqj, 2bqk, 2bql, 2bqm, 2bqn, 2bqo, 2hea, 2heb, 2hec, 2hed, 2hee, 2hef, 2lhm, 2mea, 2meb, 2mec, 2med, 2mee, 2mef, 2meg, 2meh, 2mei, 2nwd, 3exd, 3lhm Identifiers Symbols LYZ; External IDs OMIM: 153450 MGI: 96897 HomoloGene: 37278 GeneCards: LYZ Gene EC number 3.2.1.17 Gene ontology Molecular function • lysozyme activity • hydrolase activity, acting on glycosyl bonds Cellular component • extracellular region • extracellular space Biological process • inflammatory response • metabolic process • cell wall catabolic process • cytolysis • defense response to bacterium RNA expression pattern More reference expression data Orthologs Species Human Mouse Entrez 4069 17105 Ensembl ENSG00000090382 ENSMUSG00000069516 UniProt P61626 Q3TXG2 RefSeq (mRNA) NM_000239 NM_017372 RefSeq (protein) NP_000230 NP_059068 Location (UCSC) Chr 12: 68.03 - 68.03 Mb Chr 10: 116.68 - 116.69 Mb PubMed search [1] [2]

Lysozyme single crystal.

Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, are a family of enzymes (EC 3.2.1.17) which damage bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrins. Lysozyme is abundant in a number of secretions, such as tears, saliva, human milk and mucus. It is also present in cytoplasmic granules of the polymorphonuclear neutrophils (PMN). Large amounts of lysozyme can be found in egg white. C-type lysozymes are closely related to alpha-lactalbumin in sequence and structure making them part of the same family.

In humans, the lysozyme enzyme is encoded by the LYZ gene.^[1][2]

[edit] Function

The enzyme functions by attacking peptidoglycans (found in the cell walls of bacteria, especially Gram-positive bacteria) and hydrolyzing the glycosidic bond that connects N-acetylmuramic acid with the fourth carbon atom of N-acetylglucosamine. It does this by binding to the peptidoglycan molecule in the binding site within the prominent cleft between its two domains. This causes the substrate molecule to adopt a strained conformation similar to that of the transition state^{[citation needed]}. According to Phillips-Mechanism, the lysozyme binds to a hexasaccharide. The lysozyme then distorts the 4th sugar in hexasaccharide (the D ring) into a half-chair conformation. In this stressed state the glycosidic bond is easily broken.

The amino acid side chains glutamic acid 35 (Glu35) and aspartate 52 (Asp52) have been found to be critical to the activity of this enzyme. Glu35 acts as a proton donor to the glycosidic bond, cleaving the C-O bond in the substrate, whilst Asp52 acts as a nucleophile to generate a glycosyl enzyme intermediate. The glycosyl enzyme intermediate then reacts with a water molecule, to give the product of hydrolysis and leaving the enzyme unchanged.

[edit] Role in disease

Lysozyme is part of the innate immune system. Children fed infant formula lack lysozyme in their diet and have three times the rate of diarrheal disease.^{[citation needed]} Since lysozyme is a natural form of protection from pathogens like Salmonella, E.coli and Pseudomonas, a deficiency due to infant formula feeding can lead to increased incidence of disease.

Whereas the skin is a protective barrier due to its dryness and acidity, the conjunctiva (membrane covering the eye) is instead protected by secreted enzymes, mainly lysozyme and defensin. However, when these protective barriers fail, conjunctivitis results.

[edit] History

Laschtschenko first described lysozyme in 1909.^[3]

Alexander Fleming (1881-1955), the discoverer of penicillin, described lysozyme in 1922.^[4]

Its structure was described by David Chilton Phillips (1924-1999) in 1965 when he got the first 2 Ångström (200 pm) resolution image.^[5][6] This work led Phillips to provide an explanation for how enzymes speed up a chemical reaction in terms of its physical structures. The original mechanism proposed by Phillips was more recently revised.^[7]

Howard Florey (1898-1968) and Ernst B. Chain (1906-1979) also investigated lysozymes. Although they never made much progress in this field, they along with Fleming developed penicillin.

[edit] See also

• Egg allergy

[edit] References

[edit] External links

• MeSH Muramidase
• "Lysozyme: enzyme, sequence, crystallization, structure". lysozyme.co.uk. http://lysozyme.co.uk/. Retrieved 2009-01-04. 
• Proteopedia.org HEW Lysozyme

v • d • e PDB Gallery 133l: ROLE OF ARG 115 IN THE CATALYTIC ACTION OF HUMAN LYSOZYME. X-RAY STRUCTURE OF HIS 115 AND GLU 115 MUTANTS   134l: ROLE OF ARG 115 IN THE CATALYTIC ACTION OF HUMAN LYSOZYME. X-RAY STRUCTURE OF HIS 115 AND GLU 115 MUTANTS   1b5u: CONTRIBUTION OF HYDROGEN BONDS TO THE CONFORMATIONAL STABILITY OF HUMAN LYSOZYME: CALORIMETRY AND X-RAY ANALYSIS OF SIX SER->ALA MUTANT   1b5v: CONTRIBUTION OF HYDROGEN BONDS TO THE CONFORMATIONAL STABILITY OF HUMAN LYSOZYME: CALORIMETRY AND X-RAY ANALYSIS OF SIX SER->ALA MUTANTS   1b5w: CONTRIBUTION OF HYDROGEN BONDS TO THE CONFORMATIONAL STABILITY OF HUMAN LYSOZYME: CALORIMETRY AND X-RAY ANALYSIS OF SIX SER->ALA MUTANTS   1b5x: Contribution of hydrogen bonds to the conformational stability of human lysozyme: calorimetry and x-ray analysis of six ser->ala mutants   1b5y: CONTRIBUTION OF HYDROGEN BONDS TO THE CONFORMATIONAL STABILITY OF HUMAN LYSOZYME: CALORIMETRY AND X-RAY ANALYSIS OF SIX SER->ALA MUTANTS   1b5z: CONTRIBUTION OF HYDROGEN BONDS TO THE CONFORMATIONAL STABILITY OF HUMAN LYSOZYME: CALORIMETRY AND X-RAY ANALYSIS OF SIX SER->ALA MUTANTS   1b7l: VERIFICATION OF SPMP USING MUTANT HUMAN LYSOZYMES   1b7m: VERIFICATION OF SPMP USING MUTANT HUMAN LYSOZYMES   1b7n: VERIFICATION OF SPMP USING MUTANT HUMAN LYSOZYMES   1b7o: VERIFICATION OF SPMP USING MUTANT HUMAN LYSOZYMES   1b7p: VERIFICATION OF SPMP USING MUTANT HUMAN LYSOZYMES   1b7q: VERIFICATION OF SPMP USING MUTANT HUMAN LYSOZYMES   1b7r: VERIFICATION OF SPMP USING MUTANT HUMAN LYSOZYMES   1b7s: VERIFICATION OF SPMP USING MUTANT HUMAN LYSOZYMES   1bb3: HUMAN LYSOZYME MUTANT A96L   1bb4: HUMAN LYSOZYME DOUBLE MUTANT A96L, W109H   1bb5: HUMAN LYSOZYME MUTANT A96L COMPLEXED WITH CHITOTRIOSE   1c43: MUTANT HUMAN LYSOZYME WITH FOREIGN N-TERMINAL RESIDUES   1c45: MUTANT HUMAN LYSOZYME WITH FOREIGN N-TERMINAL RESIDUES   1c46: MUTANT HUMAN LYSOZYME WITH FOREIGN N-TERMINAL RESIDUES   1c7p: CRYSTAL STRUCTURE OF MUTANT HUMAN LYSOZYME WITH FOUR EXTRA RESIDUES (EAEA) AT THE N-TERMINAL   1cj6: T11A MUTANT HUMAN LYSOZYME   1cj7: T11V MUTANT HUMAN LYSOZYME   1cj8: T40A MUTANT HUMAN LYSOZYME   1cj9: T40V MUTANT HUMAN LYSOZYME   1ckc: T43A MUTANT HUMAN LYSOZYME   1ckd: T43V MUTANT HUMAN LYSOZYME   1ckf: T52A MUTANT HUMAN LYSOZYME   The maximum number of images (30) is exceeded !