Question

Give one reason why lysozyme is considered an enzyme and not a hormone. How does it defend the body? Name any two secretions in the human body which contain lysozyme?

Answer 1

There is a difference between an enzyme and hormone. An enzyme functions as a catalyst and speeds up both the rate and enhances the specificity of metabolic reactions. While hormones are the chemicals released by a cell or a gland in one part of the body that further travels and affects cells in other parts of the organism.

Complete answer:
Lysozyme is said to be an enzyme and not hormone because of few reasons: -
Reason is that Lysozyme is an enzyme that destroys bacteria by breaking the links between the molecules forming the peptidoglycan layer and thus damaging the bacterial cell wall. It primarily plays a role in invading the bacteria. It can be found in tears, saliva, sweat, and other body fluids. The mucosal linings like the nasal cavity also contain lysozyme.
It also acts as a defense system. It destroys bacteria that constantly tries to enter the body. Tears protect our eyes from bacteria that tries to enter our eyes. Lysozyme breaks the chemical bonds in the outer cell wall of the bacteria. Bacterial cell walls are composed of peptidoglycan that the lysozyme targets. The peptidoglycan has alternating molecules termed as 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.
As soon as the chain is broken by lysozyme, it causes bacterial death.
Saliva and tears are secretions of the human body that contain lysozyme.

Note: Lysozyme, one of the most powerful natural antibacterial and antiviral compounds known to man, has been used in foods and pharmaceuticals as it has the ability to naturally inhibit the growth of many spoilage organisms which then improves the shelf life. It also boosts the immune system. Human lysozyme is an important enzyme which is part of the human body's defense against some bacteria. It is found in abundance in tears, saliva and mucous. Also, there are no subunits and no prosthetic groups present in the enzyme.