Explore acid is cleaved by lysozyme. Once this

Explore what makes the lysozyme enzyme a powerful antibacterial agent. Learn about lysozyme’s intriguing discovery and how it works to protect our body from harm.

The Discovery of Lysozyme

Magical tears: They are often portrayed in fairy tales as the life-giving savior of the prince in distress.

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But, what if there really was a little magic in our tears? Actually, our tears contain a powerful, unique enzyme called lysozyme that can protect our body from harm.Lysozyme is a special enzyme found in tears, saliva, sweat, and other body fluids. Other mucosal linings, such as the nasal cavity, also contain lysozyme. It destroys bacteria that attempt to enter our body through these passageways. In the case of tears, they protect our eyes from bacterial invaders.

Don’t worry, you don’t have to cry for this protection to work: there’s already a tear film, or liquid layer, that coats the eyes to keep them safe.It was the famous scientist Alexander Fleming who discovered lysozyme in the early twentieth century. While growing a bacterial culture, a drop of mucus from his nose fell into the culture.

Eventually, he noticed that the bacteria in this culture had been killed. He named the substance lysozyme by combining two words: ‘lyse’ and ‘enzyme’.

Lysozyme as an Antibacterial Agent

Lysozyme is capable of breaking the chemical bonds in the outer cell wall of the bacteria. Bacterial cell walls contain a layer of peptidoglycan, which is the specific site that lysozyme targets. The peptidoglycan layer contains alternating molecules called N-acetylglucosamine and N-acetylmuramic acid. These molecules form a strong glycan chain that act as the backbone for the cell wall. The link between the N-acetylglucosamine and N-acetylmuramic acid is cleaved by lysozyme.

Once this chain is broken by lysozyme, it results in bacterial death.On a gram-positive bacteria, this peptidoglycan layer is on the outermost surface of the cell. However on a gram-negative bacteria, the peptidoglycan layer of the cell wall is located further inward. For this reason, lysozyme can more readily destroy gram-positive bacteria than gram-negative bacteria.

The Structure of Lysozyme

Imagine that you were in the outfield playing baseball, waiting for a hit to come your way.

But you aren’t going to catch the ball with your bare hands. To better your chances of trapping the ball, you’re going to use a glove with a large pocket to catch the ball.The glove structure is similar to that of lysozyme enzyme. Lysozyme has a prominent cleft that it uses to ‘catch’ its ‘ball’, or its substrate. The substrate is the molecule with which an enzyme binds. In the case of the lysozyme enzyme, the substrate is the N-acetylglucosamine and N-acetylmuramic acid. Lysozyme hydrolyzes, or breaks, the links in the peptidoglycan glycan chain.

Lysozyme in Foods

Lysozyme is not only found in our body, but is also an important enzyme found in egg whites. If there is a breakage in the protective outer shell of the egg, bacteria may enter through this site. The lysozyme in the egg white will attempt to destroy the bacteria before spoilage occurs. Hen egg white (HEW) lysozyme is a well-studied protein and has been proven a very powerful enzyme.

Lesson Summary

As it turns out, our tears do contain some magic, namely the powerful enzyme lysozyme.

This enzyme is crucial in thwarting bacteria that attempts to enter our body cavities. By destroying the peptidoglycan layer of bacterial cell walls, it serves as a strong chemical defense against bacterial infections.Part of the lysozyme structure entails a large cleft to ‘catch’ its substrate.

The substrate, or ‘ball’ that lysozyme ‘catches, are the N-acetylglucosamine and N-acetylmuramic acid molecules located in the peptidoglycan layer of the cell wall. Lysozyme binds to this chain and cleaves the link between these two molecules, leading to bacterial cell death.

Lysozyme Key Terms ; Events

Lysozyme in Tears
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  • Dr. Alexander Fleming: Scientist who in early 1900s discovered lysozyme
  • Lysozyme: Enzyme in tears, sweat, saliva that destroys certain bacteria
  • Peptidoglycan: Layer of a bacteria’s cell wall
  • N-acetylglucosamine/N-acetylmuramic Acid: Molecules located within the bacteria cell walls

Learning Outcomes

After this lesson is over, students should be able to:

  • Recall how lysozyme was discovered
  • Define the various terms describing the cell parts
  • Illustrate how lysozyme kills bacteria cells
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