Index
It is an antimicrobial enzyme found in humans and in a wide variety of organisms, including birds, mammals, plants, insects, and bacteria.
The lysozyme in chicken egg white has been studied more extensively.
History about lysozyme
Chicken egg lysozyme was first described by Laschtschenko in 1909. It was also reported in saliva by Bloomfield in 1919 (Imoto et al. 1972).
Lysozyme was not officially named and understood as present in many biological tissues and secretions until 1922 (Fleming 1922).
During these experiments, Alexander Fleming discovered Micrococcus lysodeikticus, a bacteria especially susceptible to lysozyme, which is still used today for lysozyme activity assays (Imoto et al. 1972).
In 1965, Blake et al. resolved the structure of lysozyme, making it the second protein structure and first enzyme to be resolved by X-ray diffraction methods (Blake et al. 1965). One year later, the mechanism was explained (Blake et al. 1966).
Throughout the 1960s and 1970s, interest in the enzyme increased as a ‘natural’ antibiotic and aided in the diagnosis of the disease (Glynn 1968, Pruzanski and Saito 1969).
Elevated levels of lysozyme were found to be present in the urine and serum of patients with leukemia (Osserman and Lawlor 1966 and Brierre et al. 1974), and in the cerebrospinal fluid of patients with a tumor of the central nervous system (Newman et al. al. 1974).
Investigation of lysozyme in the 1980s included investigation of enzyme intermediates (Acharya 1982, Desmadril and Yon 1984 and Ikegudri et al. 1986), analyzing protein structure (Delepierre 1982) and conducting binding studies (Nutta et al. al. 1988, Perraudin and Preels 1982 and Smitth-Gill et al. 1984).
In the 1990s, additional transcriptional control, silencers, and binding sites were investigated (Bonifer et al. 1997, Baniahmad et al. 1991, and Madhusudan and Vijayan 1992).
Recent research has focused on obtaining more information on the gene regulation of lysozyme both in the hen and in other animals (Shimizu et al. 2005), obtaining a better understanding of the secondary structure (Schwinté et al. 2002) and refining its use in biochemical applications. (Reischl 2004 and Zhu 2006).
Specificity
Lysozyme hydrolyzes the beta-glucosidic bond between N-acetylmuramic acid and N-acetyl glucosamine in the peptidoglycan of bacterial cell walls and can also bind N-acetyl glucosamine polymers (Arnheim et al. 1972).
Molecular characteristics
Mature chicken lysozyme is made up of 128 amino acids. The amino acid sequences of other avian lysozymes are homologous in sequence and differ only by 4 to 20 amino acids (Arnheim et al. 1973). The lysozyme gene in chickens is expressed tissue specifically in the oviduct and macrophages.
Although there is only one copy of the lysozyme gene, it is regulated differently in the oviduct and macrophages.
Regulation of lysozyme in the oviduct uses steroid hormones, while a combination of cis regulatory elements is used during differentiation into macrophages (Shimizu et al. 2005).
Transcription is controlled by three enhancers, a complex promoter and a negative regulatory element (Bonifer et al. 1997, and Lefevre et al. 2008).
Composition of lysozyme
The structure of lysozyme is consistent under a variety of conditions, making it ideal for crystallographic studies. The active site of lysozyme consists of a deep cleft, which divides the protein into two domains joined by an alpha helix.
One domain (residues 40 to 85) consists almost entirely of a beta sheet structure, while the second domain (residues 89-99) is more helical (Strynadka and James 1991).
- Protein Accession Number: P00698.
CATH classification (v. 3.2.0):
- Class: mainly alpha
- Architecture : orthogonal package.
- Topology : lysozyme.
- Molecular weight : 14.3 kDa (theoretical).
- Optimal pH : 6.0-9.0 (Davis et al. 1969).
- Isoelectric point : 9.32 (theoretical).
Extinction coefficient:
- 38,940 cm -1 M -1 (Teórico)
- And 1%, 280 = 27.21 (theoretical)
Active site residues:
- Glutamic acid (E53).
- Aspartic acid (D70).
Activators:
- EDTA (White and white 1997).
- Inhibitors
- SDS.
Alcohols
- N- acetyl- D- glucosamine.
Applications of lysozyme
- Nucleic acid preparation (Taylor and Utter 1974).
- Inclusion body protein purification (Reischl 2004).
- Plasmid preparation (to break down cell walls and membranes) (Zhu 2006).
- Chitin hydrolysis (Hayashi et al. 1969).
- Hydrolysis of bacterial cell walls (Shockman et al. 1996).
