Lysozyme is best described as which type of antimicrobial agent?

• A. Enzyme that cleaves peptidoglycan
• B. Antibody that neutralizes toxins
• C. Cytokine
• D. Complement component

Answer: (A)

Lysozyme is an antimicrobial enzyme. It works by hydrolyzing the β-1,4 glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan, weakening the bacterial cell wall and causing lysis, especially in gram-positive bacteria with thick peptidoglycan layers. This enzymatic activity is found in secretions like tears and saliva, and it operates as part of innate defense. Because it acts by cleaving cell-wall components rather than binding antigens or signaling molecules, it is best described as an enzyme that cleaves peptidoglycan. It is not an antibody, which neutralizes toxins or pathogens via antigen binding; not a cytokine, which mediates immune signaling; and not a complement component, which participates in the complement cascade.