X Международный конкурс научно-исследовательских и творческих работ учащихся
Старт в науке
Лизоцим и его внезапное открытие
Автор работы награжден дипломом победителя I степени
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Introduction
In antiquity it was considered that tears could heal. Heroes were cured by young ladies’ tears. However their medicinal properties originally were confirmed by Alexander Fleming, who was a Scottish biologist and pharmacologist. He discovered lysozyme in 1921 and then penicillin in 1928.
Figure №1: Alexander Fleming
So his first discovery was lysozyme. It is an antiviral and antimicrobial enzyme.
LYSOZYME
LYSIS ENZYME
An enzyme that catalyzes the destruction of the cell walls of certain bacteria, occurring notably in tears and egg white.
Lysozyme, one of the most powerful natural antibacterial and antiviral compounds known to man, has been used in foods and pharmaceuticals for over three decades as it naturally inhibits the growth of many spoilage organisms, increases healthy shelf life and ensures food safety. It also boosts the immunity system.
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The discovery
Fleming always had been leaving his growths for over two weeks and then scrutinizing them carefully to check whether there was something new.
One day he sowed mucus from his own nose on a Petri dish with bacteria. Some days after the scientist saw, he eliminated bacteria in places where mucus was inflicted.
He inferred immediately that the substance,staying in that mucus, was dissolved nearby microbes. Then extending (spreading), it affected colonies.
Later experimentations showed that the substance was present in tears, too.
Figure №2: Fleming’s growth.
Why do natural secretions of organism possess such bactericidal properties?
From birth organism is contacted with infinite amount of microbes, that penetrating into nose, mouth and intestine. Why are not people dying then? Because vulnerable body parts are protected. Blood with phagocytes provides this defense. However, some parts of the body are not protected from falling microbes into organism from air.
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Alexander Fleming proved lysozyme is one of the natural protection gear and confirmed that this substance is found in all living organisms:
Lysozyme
Figure №3: Species where lysozyme occurs
The chemistry behind lysozyme
Lysozyme is a key element in the immune system's fight against infection. This natural polypeptide with a molecular weight of 14,3kDa is found in the organs and bodily fluids of humans, animals, and plants. Lysozyme is naturally present in and can be isolated from mother's milk, tears, saliva, and even cauliflower juice.
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It is also known as muramidase, are small globular protein enzymes composed of 129 amino acid residues. As one of the first enzymes to be studied, Alexander Fleming had shown them to be produced by phagocytes and epithelial cells.
Phagocytes move and struggle with foreign substances, they can even devour cancer cells. As for epithelial, they produce biologically active compounds that destroy pathogenic germs. Therefore, lysozyme is inside them.
Antibacterial features of this enzyme is effectively rupturing the peptidoglycan layer of the cell wall. Peptidoglycan layer is a component of bacteria’s cell wall that carries out mechanic functions, antigen functions.
The most interesting thing that there is no addiction using lysozyme for pathogen organisms. That is why it is efficient method to handle.
Figure №4: Muramidase
Protection mechanism
A bacterium, protected by its peptidoglycan cell wall. The zoom shows the fairly regular architecture of the cell wall, built from NAM (N-acetyl muramic acid) and NAG (N-acetyl glucosamine) sugar units. The bacterial cell wall is further strengthened by cross-linking peptides.
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Figure №5: The cell wall
Lysozyme binding to the bacterial cell wall; note the nearly perfect fit except at position D where the NAM unit is strained, creating a weakened link and a site where lysozyme can cut the sugar chain of the bacterial cell wall.
Figure №6: The mechanism of the attack
Death of the bacterial cell by explosion, from inflow of water into the cell and corresponding increased intra-cell pressure.
Figure №7: Death of the bacterial cell
Why is lysozyme not toxic to human health? Why does not it destroy human membrane?
Any membrane has its own receptors. Lysozyme contacts only with foreign receptors.
Applications
The chemistry of lysozyme and its use as a food preservative and a pharmaceutical
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Lysozyme has been used to preserve fresh fruits and vegetables, seafood, meats and sausages, potato salad, cooked burdock with soy sauce, and varieties of cheeses such as Edam, Gouda, and some Italian cheeses.
Lysozyme added to infant-feeding formulas makes them more closely resemble human milk. Lysozyme has been used clinically in the treatment of periodontitis, administered in chewing gum, and implemented to prevent tooth decay.
It has also been administered to patients suffering from cancer for its analgesic effect and has been used as a potentiating agent in antibiotic therapy.
Lysozyme has been added to baby formula (to aid digestibility) and gastrointestinal treatments for the elderly. Lysozyme is used in skincare, to cure and prevent acne and bedsores, as well as in optical and oral conditions.
Figure №8: Practical application
Interesting facts
Honey
Honeycomb is healthier than liquid honey.
Every honeycomb contains honeyand lysozyme. This is the healthiest liquid substance.
Honey in honeycombs is the best substitution to things "for strengthening immunity" and it is natural. But the most important source from which lysozyme can be extracted on an industrial scale is chicken albumen.
Chicken albumen
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Eggs possess strong bactericidal properties that are important. Albumen and even egg yolk are excellent environment for cultivation microbes. Eggshell is not a barrier for them.
Furthermore, eggs can lie for more than a week in shopping malls, where they face impact of different microorganisms. Nevertheless, they stay sterile due to protective functions.
Probably, places, which are more open for infection, at the same time, are better protected. For example, rainworms are known to secrete mucus, which is highly bactericidal.
Conclusion
As a matter of fact, lysozyme played the role of a natural sanitizer – the first line of a cell wall defense against microbes.
Alexander Fleming had every right to be proud of his findings. He discovered a brand new and significant way of organism protection. Before him, the scientist Ilya Mechnikov proved that phagocytes could prevent microbes from attacking an organism. And Fleming was the one who stated that the cells contained lysozyme.
Thanks to their work,nowadays, people use lysozymein different areasof life. In medicine, in food and even in electricity this ferment is essential. Lysozyme can develop power with mechanic exposure, defend our organism and prevent acne. We cannot currently imagine our life without it.
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References
https://www.bioseutica.com/source/lysozyme
2.https://biography.wikireading.ru/91860
3. https://businessviews.com.ua/ru/personal-life/id/5-vazhnyh-faktov-o-mede-o-kotoryh-vy-ne-zadumyvalis-341/
4. https://www.britannica.com/science/lysozyme
5. https://maxfacts.uk/help/oral-hygiene/saliva-and-teeth-mucosa