Lysozyme

LYZmuramidaselysozymesE1105human lysozymeT4 lysozyme
Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, is an antimicrobial enzyme produced by animals that forms part of the innate immune system.wikipedia
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Innate immune system

innate immunityinnateinnate immune response
Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, is an antimicrobial enzyme produced by animals that forms part of the innate immune system.

Glycoside hydrolase

Glycoside hydrolasesglycosidaseglycosidases
Lysozyme is a glycoside hydrolase that catalyzes the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan, which is the major component of gram-positive bacterial cell wall.
They are extremely common enzymes with roles in nature including degradation of biomass such as cellulose (cellulase), hemicellulose, and starch (amylase), in anti-bacterial defense strategies (e.g., lysozyme), in pathogenesis mechanisms (e.g., viral neuraminidases) and in normal cellular function (e.g., trimming mannosidases involved in N-linked glycoprotein biosynthesis).

Tears

lacrimationteartear film
Lysozyme is abundant in secretions including tears, saliva, human milk, and mucus.
Tears are composed of water, salts, antibodies and lysozymes (antibacterial enzymes), though composition varies among different tear types.

Mucus

mucousmucinousslime
Lysozyme is abundant in secretions including tears, saliva, human milk, and mucus.
It is a viscous colloid containing inorganic salts, antimicrobial enzymes (such as lysozymes), immunoglobulins, and glycoproteins such as lactoferrin and mucins, which are produced by goblet cells in the mucous membranes and submucosal glands.

Saliva

salivationspittlespit
Lysozyme is abundant in secretions including tears, saliva, human milk, and mucus.
In humans, saliva is 99.5% water plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (such as amylase and lipase), antimicrobial agents such as secretory IgA, and lysozymes.

Lysis

lysecell lysislysed
This hydrolysis in turn compromises the integrity of bacterial cell walls causing lysis of the bacteria.
Many species of bacteria are subject to lysis by the enzyme lysozyme, found in animal saliva, egg white, and other secretions.

Glycoside hydrolase family 22

C-type lysozymes are closely related to alpha-lactalbumin in sequence and structure, making them part of the same glycoside hydrolase family 22.
Glycoside hydrolase family 22 CAZY GH_22 comprises lysozyme type C lysozyme type i and alpha-lactalbumins.

Macrophage

macrophagesM2 macrophagesTissue macrophages
It is also present in cytoplasmic granules of the macrophages and the polymorphonuclear neutrophils (PMNs).
They can be identified using flow cytometry or immunohistochemical staining by their specific expression of proteins such as CD14, CD40, CD11b, CD64, F4/80 (mice)/EMR1 (human), lysozyme M, MAC-1/MAC-3 and CD68.

Breast milk

human milkhuman breast milkbreastmilk
Lysozyme is abundant in secretions including tears, saliva, human milk, and mucus.
The principal proteins are alpha-lactalbumin, lactoferrin (apo-lactoferrin), IgA, lysozyme, and serum albumin.

Gram-negative bacteria

Gram-negativeGram negativeGram-negative bacterium
In Gram-negative bacteria, the lipopolysaccharide acts as a non-competitive inhibitior by highly-favored binding with lysozyme.
They are an important medical challenge, as their outer membrane protects them from many antibiotics (including penicillin); detergents that would normally damage the peptidoglycans of the (inner) cell membrane; and lysozyme, an antimicrobial enzyme produced by animals that forms part of the innate immune system.

Neutrophil

neutrophilsneutrophil granulocyteneutrophilic
It is also present in cytoplasmic granules of the macrophages and the polymorphonuclear neutrophils (PMNs).

Peptidoglycan

mureinpeptidoglycanspeptidoglycan layer
Lysozyme is a glycoside hydrolase that catalyzes the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan, which is the major component of gram-positive bacterial cell wall. The enzyme functions by attacking, hydrolyzing, and breaking glycosidic bonds in peptidoglycans.
Lysozyme, which is found in tears and constitutes part of the body's innate immune system exerts its antibacterial effect by breaking the β-(1,4)-glycosidic bonds in peptidoglycan (see above).

Alexander Fleming

Sir Alexander FlemingFlemingAlex Fleming
The antibacterial property of hen egg white, due to the lysozyme it contains, was first observed by Laschtschenko in 1909, although it was not until 1922 that the name 'lysozyme' was coined, by Alexander Fleming, the second scientist to discover penicillin.
His best-known discoveries are the enzyme lysozyme in 1923 and the world's first antibiotic substance benzylpenicillin (Penicillin G) from the mould Penicillium notatum in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Howard Florey and Ernst Boris Chain.

Alpha-lactalbumin

α-lactalbumina-Lactalbuminalpha
C-type lysozymes are closely related to alpha-lactalbumin in sequence and structure, making them part of the same glycoside hydrolase family 22.
The sequence comparison of α-lactalbumin shows a strong similarity to that of lysozymes, specifically the Ca 2+ -binding c-lysozyme.

David Chilton Phillips

David PhillipsDavid Chilton Phillips, Baron Phillips of EllesmereD. C. Phillips
Lysozyme was first crystallised by Edward Abraham in 1937, enabling the three-dimensional structure of hen egg white lysozyme to be described by David Chilton Phillips in 1965, when he obtained the first 2-ångström (200 pm) resolution model via X-ray crystallography.
Phillips was the first person to determine in atomic detail the structure of the enzyme lysozyme, which he did in the Davy Faraday Research Laboratories of the Royal Institution in London in 1965.

Spheroplast

spheroplastsscreensphaeroplasts
Due to the unique function of lysozyme in which it can digest the cell wall and causes osmotic shock (burst the cell by suddenly changing solute concentration around the cell and thus the osmotic pressure), lysozyme is commonly used in lab setting to release proteins from bacterium periplasm while the inner membrane remains sealed as vesicles called the spheroplast.
The enzyme lysozyme causes Gram-negative bacteria to form spheroplasts, but only if a membrane permeabilizer such as lactoferrin or ethylenediaminetetraacetate (EDTA) is used to ease the enzyme’s passage through the outer membrane.

Enzyme

enzymologyenzymesenzymatic
The enzyme functions by attacking, hydrolyzing, and breaking glycosidic bonds in peptidoglycans.
This was first done for lysozyme, an enzyme found in tears, saliva and egg whites that digests the coating of some bacteria; the structure was solved by a group led by David Chilton Phillips and published in 1965.

Antimicrobial

anti-microbialantimicrobialsantimicrobial agent
Lysozyme, also known as muramidase or N-acetylmuramide glycanhydrolase, is an antimicrobial enzyme produced by animals that forms part of the innate immune system.

Hydrolysis

hydrolyzedhydrolysehydrolyze
Lysozyme is a glycoside hydrolase that catalyzes the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan, which is the major component of gram-positive bacterial cell wall.

Gram-positive bacteria

Gram-positiveGram positivegram-positive bacterium
Lysozyme is a glycoside hydrolase that catalyzes the hydrolysis of 1,4-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in peptidoglycan, which is the major component of gram-positive bacterial cell wall.

Secretion

secretedsecretory pathwaysecrete
Lysozyme is abundant in secretions including tears, saliva, human milk, and mucus.

Cytoplasm

cytoplasmiccytosolicintracytoplasmic
It is also present in cytoplasmic granules of the macrophages and the polymorphonuclear neutrophils (PMNs).

Melting point

freezing pointmelting temperaturemelting
Hen egg white lysozyme is thermally stable, with a melting point reaching up to 72°C at pH 5.0.

Isoelectric point

pIiso-electric pointisoelectric point (pI)
Its isoelectric point is 11.35.

Glycosidic bond

glycosidic linkageglycosidic bondsglycosidic
The enzyme can also break glycosidic bonds in chitin, although not as effectively as true chitinases.