Question

The antimicrobial agent mercuric chloride functions by

• A. Interfering with cellular oxidation process.
• B. Inhibiting the enzymes which contain the sulfhydryl group.
• C. Alkylation reactions with organic compounds such as enzymes and other proteins.
• D. Denaturation of proteins, interference with glycolysis and membrane damage.

Hint:

Remember that heavy metals like mercury, silver, and arsenic are "sulfhydryl seekers." They poison cells by attacking the -SH groups in proteins, effectively shutting down vital enzymes.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Mercuric chloride (\(HgCl\(_2\)\)) is a potent antimicrobial heavy metal compound. Heavy metals are toxic because they bind to and deactivate essential cellular proteins, particularly enzymes.
Step 2: Detailed Explanation:


Heavy metal ions like mercury (\(Hg\)^{2+}\)) act primarily by binding to sulfhydryl (-SH) groups in the amino acid cysteine.

\(Hg\)^{2+}\) binding to protein sulfhydryl groups creates a stable mercaptide (Protein-S-Hg-S-Protein).

This binding disrupts the protein's structure and inactivates its active site, particularly in enzymes where cysteine is critical for catalysis. This is sulfhydryl group inhibition.

While general protein denaturation (Option D) is possible at high concentrations, the main mechanism at biocidal concentrations is targeted inhibition of sulfhydryl-containing enzymes.

Option C, alkylation, is how agents like ethylene oxide work. Option A is too broad.

Step 3: Final Answer:
Mercuric chloride's primary antimicrobial action is enzyme inhibition via sulfhydryl group binding.