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What is Lysozyme?

Lysozyme is a natural enzyme, a powerful defender found in human tears, saliva, and milk, that attacks and breaks down bacterial cell walls. This unsung hero of our immune system is crucial for warding off infections. Intrigued by how this microscopic warrior keeps you healthy? Discover its secrets and the science behind its protective power in our detailed visual journey. Ready to explore?
Helga George
Helga George

Lysozyme is a protein found in tears, saliva, and other secretions. It can degrade the cell walls of certain kinds of bacteria and acts as a natural antibiotic. This protein is also found in egg white and is one of the major contributors to egg allergies.

While most of the body is protected by a covering of skin, the eyes and mucus membranes do not have this protection. Lysozyme is produced in tears and mucus secretions to protect these areas against invasion by bacteria. It is also present in the blood to help keep bacteria from being spread throughout the body. This protein is part of the immune system and is also found in human milk. It is passed to children through breast-feeding, helping them to establish their immune system.

Lysozyme helps protect the eyes from bacteria.
Lysozyme helps protect the eyes from bacteria.

Eggs from hens have a large quantity of this protein in their whites, which are more prone to cause allergies than the yolks. It is one of the top four proteins in the egg white to which people who have food allergies from eggs have the strongest allergic response. There is no treatment for this, except for scrupulously avoiding egg products, which can be a difficult process. Even the anesthetic propofol contains egg lecithin.

Lysozyme is a protein found in egg whites.
Lysozyme is a protein found in egg whites.

Lysozyme is of historical interest, since it was the first antibacterial substance discovered. Sir Alexander Fleming, who went on to discover penicillin, had a cold and put a drop of mucus on a plate of bacteria. He discovered that the mucus killed the bacteria, but the molecule is too large to be practical as a drug. Many years later, this protein was the first enzyme to have its three-dimensional structure solved.

Lysozyme is passed to a child via breast-feeding to help develop the immune system.
Lysozyme is passed to a child via breast-feeding to help develop the immune system.

The manner in which lysozyme protects against bacterial invasion is through its activity as an enzyme — an agent that speeds up reactions. The bacteria affected have polysaccharides in their cell walls that are chains of sugars with side chains that contain amine, NH2, groups. The protein degrades these polysaccharides by adding a molecule of water to the sugar linkage, causing it to break open. This is known as glycoside hydrolase, or water breakdown of sugar. Once the polysaccharide chain is disrupted, the bacterial cells burst.

There are several types of lysozymes found in a variety of different organisms, forming a family of enzymes. In humans, the gene is known as the LYZ gene. Another term for the enzyme is muramidase, because it cleaves the bond that connects N-acetylmuramic acid to its adjoining sugar molecule. The technical name for the enzyme is N-acetylmuramide glycanhydrolyase.

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Discussion Comments


I agree with StarJo. Adding more chemicals to our food is not the answer. Although we may be able to produce more 'safe' food for the masses in the short term, in the long term biologically and chemically altering our food has been proven to only cause more problems for the population. meaning more allergic reactions and higher health care costs.


@DylanB – I hope it doesn't! I am allergic to egg whites, and this would mean it would be dangerous for me to even eat the vegetables that were treated with the lysozyme.

My body thinks that this protein is an invader, so it starts freaking out if I eat anything containing egg whites. I start wheezing and coughing, and I even break out in hives. Breathing becomes difficult, and I have to take a couple of antihistamines right away.

I doubt that scientists will ever encourage the use of egg white lysozymes to prevent bacteria growth in food, knowing that many people have this allergy. If they do, then food labels will have to clearly state an allergy warning.


I heard about a study in which scientists added egg white lysozyme to several different types of food to see if it would kill bacteria. I think they were probably amazed when they found that it did, because I know that I was.

They tested vegetables like carrots and corn and also some types of meat and cheese. Though the lysozyme wasn't quite as effective in killing all the bacteria in the cheese and meat, it did kill some, and it worked wonders with the vegetables.

So, egg white lysozyme could be used to help kill the bacteria that causes food poisoning. I've had this before, and all that vomiting and diarrhea is not something I ever want to experience again, so I hope this becomes an accepted practice.


I always thought that all mucus did to fight bacteria was capture it in the nostrils and bronchial tubes and keep it from getting any deeper into your body. I didn't know that it actually contained antibacterial protein!

So, every time that I have had an extremely runny nose during a sickness, all that mucus was actually worth something. I always considered it a curse and a huge nuisance, but now, I will be able to appreciate it more.

When Sir Alexander Fleming first saw his mucus attack bacteria, he must have been thrilled. Imagine making such a discovery as a result of your sniffling misery!

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    • Lysozyme helps protect the eyes from bacteria.
      By: Serg Zastavkin
      Lysozyme helps protect the eyes from bacteria.
    • Lysozyme is a protein found in egg whites.
      By: Elenathewise
      Lysozyme is a protein found in egg whites.
    • Lysozyme is passed to a child via breast-feeding to help develop the immune system.
      By: drubig-photo
      Lysozyme is passed to a child via breast-feeding to help develop the immune system.