Which enzyme, found in bodily secretions such as tears and saliva, functions as an antimicrobial agent by cleaving the peptidoglycan component of bacterial cell walls?

The enzyme that functions as an antimicrobial agent by cleaving the peptidoglycan component of bacterial cell walls is lysozyme. Lysozyme is widely distributed in bodily secretions such as tears, saliva, and mucus, where it plays a crucial role in the body's innate immune response.

By breaking down the peptidoglycan layer, which is a critical structural component of bacterial cell walls, lysozyme compromises the integrity of the bacteria, ultimately leading to cell lysis and death. This mechanism is particularly effective against Gram-positive bacteria, which have thick peptidoglycan layers.

The other enzymes listed, such as pepsin, amylase, and trypsin, have different functions. Pepsin is a proteolytic enzyme involved in digesting proteins in the stomach, amylase is responsible for breaking down starches, and trypsin also functions as a protease but is active in the small intestine. None of these enzymes possess the antibacterial function that lysozyme does. Thus, the identification of lysozyme as the correct answer highlights its important role in antimicrobial defense within the human body.