Enzymatic lysis: the cell walls of many Gram-positive bacteria are readily destroyed by which enzyme that hydrolyzes the NAG–NAM linkage?

Introduction / Context:Understanding how host defenses and laboratory reagents disrupt bacterial walls is central to microbiology. Lysozyme is a natural antimicrobial enzyme found in tears, saliva, and other secretions that targets a specific bond in peptidoglycan.

Given Data / Assumptions:

• We seek the enzyme that efficiently damages Gram-positive cell walls.
• Consider the thick peptidoglycan layer of Gram-positive bacteria as the substrate.

Concept / Approach:Lysozyme cleaves the β-1,4-glycosidic bond between N-acetylglucosamine and N-acetylmuramic acid in peptidoglycan. Gram-positive bacteria, with their exposed thick peptidoglycan (no outer membrane), are especially susceptible. Gram-negative bacteria are relatively protected by the outer membrane barrier.

Step-by-Step Solution:

Verification / Alternative check:Clinical and lab practice exploit lysozyme for spheroplast/protoplast preparation and as a component of innate immunity; its activity aligns with Gram-positive susceptibility.

Why Other Options Are Wrong:

• Lipase: acts on lipids, not peptidoglycan.
• Pectinase: acts on plant pectins, not bacterial walls.
• Peroxidase: catalyzes redox reactions; not a wall hydrolase.

Common Pitfalls:Assuming all antimicrobial enzymes target membranes; lysozyme specifically targets the carbohydrate backbone of peptidoglycan.

Final Answer:lysozyme