Description
Lysozyme is an antibacterial enzyme naturally present in animals and humans as a component of the innate immune system to fight against microorganisms. It belongs to a group of enzymes that are known as glycoside hydrolases. It is found in animal tissues, organs, serum as well as in tears, nasal secretions, cervical mucus, and the white of avian eggs. Lysozyme breaks the carbonhydrate chains of the bacterial skin, destroying the structural integrity of the cell wall. Thereby, it has antibacterial properties and was one of the first antibiotics studied by Sir Fleming, the discover of penicillin.
Lysozyme is used either alone or in combination with other synergic compounds as an excellent preservative against many food spoiling microorganisms for fruits & vegetables, tofu & bean curd, seafood & meats, wines & sakes. Organic wines use it to reduce sulfites. It is used in non-pasteurized beer. It has been added to baby formula (to aid digestibility) and gastrointestinal treatments for the elderly. Lysozyme is used in skin care, to cure and prevent acne and bed sores, as well as in optical, dental, and oral conditions.
Chemical Properties
Lysozyme (muramidase) hydrolyzes preferentially the beta-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. A somewhat more limited activity is exhibited towards chitin oligomers. Lysozyme is of widespread distribution in animals and plants. That which has been most extensively studied is from hen egg white (lysozyme C). Lysozyme is also found in mammalian secretions and tissues, saliva, tears, milk, cervical mucus, leukocytes, kidneys, etc. Lysozyme is inhibited by surface-active reagents such as dodecyl sulfate, alcohols and fatty acids. Imidazole and indole derivatives are inhibitors via formation of change-transfer complexes. Useful for the rapid isolation of RNA from gram negative bacteria. Can be used to prepare small amounts of plasmid DNA.
History
Lysozyme was first reported by the French scientist Charles Nicolet in 1907, who identified a dissolving factor in Bacillus subtilis and demonstrated that microbial cell walls could be degraded by a specific substance. In 1909, Laschtschenko observed the strong antibacterial properties of egg white and hypothesized that this activity was due to an enzyme. It was not until 1922 that the British microbiologist Alexander Fleming identified potent lysozyme activity in human secretions such as saliva and tears, and formally named it "lysozyme". Through experiments, he showed that this enzyme could lyse various bacteria, especially Gram-positive ones. Fleming gained worldwide fame in 1928 for his discovery of penicillin. Lysozyme is categorized based on its origin into chicken-type, goose-type, invertebrate-type, plant-derived, microbially derived, and other varieties.
Characteristics
Lysozyme is a white crystalline substance and an alkaline protein with an isoelectric point of pH 10.5–11.0. The product has an activity of ≥ 20,000 U/mg, dissolves in dilute saline, and forms precipitates when exposed to acetone or ethanol. It remains relatively stable in acidic solutions and is unaffected by heating to 55 °C. Its aqueous solution is completely inactivated at 62.5 °C after 30 minutes, whereas a 15% ethanol solution remains active at 62.5 °C for 60 minutes, and a 20.5% ethanol solution remains active at the same temperature for 20 minutes. Lysozyme lyses bacterial cells, showing particular effectiveness against cocci, and exhibits various antibiotic properties. These effects result from its ability to hydrolyze polysaccharides in the glycoproteins (mucin-like proteins) of cell membranes, such as chitin and ethylene glycol chitin, producing carbonate, chloride, and nitrate crystals.
Uses
Lysozyme is used to monitor transcription via real-time PCR and in sample preparation. It catalyzes the hydrolysis of peptidoglycans in bacterial cell walls and is utilized in the production of spheroplasts. Additionally, it serves as a preservative against many food-spoiling microorganisms and is applied in skincare to treat and prevent acne and bed sores, as well as in dental and oral care. Lysozyme is also used to lyse E. coli and Streptomycetes for extraction purposes, such as isolating group-specific antigens. Furthermore, it is used in non-pasteurized beer.
Application
Lysozyme from chicken egg white has been used for the extraction of genomic DNA from bacterial cells.It has been used as an external standard for MALDI-TOF (matrix assisted laser desorption ionization-time of flight) mass analysis.
Enzyme breaks down the cell walls of bacteria; used to prepare spheroplasts.
General Description
Lysozyme from chicken egg white, is a protein that can show broad spectrum of antibacterial activity against gram positive and gram negative bacteria. Its antimicrobial activity can be enhanced by pretreatment of the target microbial cells with chelating agents like ethylenediaminetetraacetic acid (EDTA).
Biochem/physiol Actions
Lysozyme 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. However, these cells may be hydrolyzed in the presence of EDTA that chelates metal ions in the outer bacterial membrane.The enzyme is active over a broad pH range (6.0 to 9.0). At pH 6.2, maximal activity is observed over a wider range of ionic strengths (0.02 to 0.100 M) than at pH 9.2 (0.01 to 0.06 M).
References
[1] RYOTA KUROKI Brian W M Larry H Weaver. A Covalent Enzyme-Substrate Intermediate with Saccharide Distortion in a Mutant T4 Lysozyme[J]. Science, 1993, 262 5142. DOI:
10.1126/science.8266098.
[2] P. E. PJURA. Structure of a thermostable disulfide-bridge mutant of phage T4 lysozyme shows that an engineered cross-link in a flexible region does not increase the rigidity of the folded protein[J]. Biochemistry Biochemistry, 1990, 29 10: 2592-2598. DOI:
10.1021/bi00462a023.
[3] D R ROSE. Crystal structure of T4-lysozyme generated from synthetic coding DNA expressed in Escherichia coli.[J]. Protein engineering, 1988, 2 4: 277-282. DOI:
10.1093/protein/2.4.277.
[4] http://ase.tufts.edu/biology/MolecVisual/bio152/rightlyso.html#top
[5] http://www.xtend-life.com/information/ingredients/lysozyme
[6] http://www.bioseutica.com/products/lysozyme
