Question

Lysozyme found in saliva, perspiration and tears destroys
A. Certain types of fungi
B. Certain types of bacteria
C. All viruses
D. Most viruses infected cells

Answer 1

Hint: This enzyme is antimicrobial and it is found in the secretions like saliva, tear, mucus, sweat and milk and since it's antimicrobial and it's clear what it destroys.

Complete answer:
First of all, you should know what Lysozyme is. Lysozyme is a naturally occurring enzyme which is found in body secretions such as tears, saliva, sweat (perspiration), milk and mucus. This enzyme is produced by animals. It plays an important role in prevention of bacterial infections. Human lysozyme is expressed in mucous membranes of the nasal cavity and tear ducts. Since it is an antimicrobial enzyme, it's action is physiological which kills certain types of bacteria by attacking, hydrolysing and breaking the glycosidic bonds in the cell wall of bacteria.

If we look at the above options,
Option A is Certain types of fungi. This option is incorrect because it is an antimicrobial enzyme and hence it kills certain types of bacteria not the fungi.

> Option B is Certain types of bacteria, this option is the correct one because it kills certain types of bacteria by attacking, hydrolysing and breaking the glycosidic bonds in the cell wall of bacteria. Therefore, this option is correct.

> Option C is All viruses, since it does not destroy any of the virus as it functions to prevent the bacterial infection therefore this cannot be the correct option.

> Option D is Most viruses infected cells. It does not destroy viruses infected cells and therefore this option cannot be correct as it destroys bacteria.

Hence, the correct answer is option (B).

Additional information:
This enzyme is a hydrolase which catalyse the hydrolysis of 1,4-B-linkages between NAG and NAM residues in peptidoglycan. NAG is N-acetyl-D-glucosamine and NAM is N-acetyl Muramic acid. Peptidoglycan is a major component of the cell wall of gram-positive bacteria.

Note: This enzyme is produced by animals in secretions like saliva, sweat, tears which functions to kill certain types of bacteria and therefore helps to prevent bacterial infection. This enzyme destroys the growth of bacteria as it breaks down the carbohydrate content of the bacterial cell wall.