Which enzyme's decrease is clinically significant?

• A. Acetylcholinesterase
• B. Amylase
• C. Lipase
• D. CK

Answer: (A)

Acetylcholinesterase is the enzyme whose decreased activity has clear clinical significance. It normally hydrolyzes acetylcholine at neuromuscular and cholinergic synapses to terminate signaling. When inhibited—most notably by organophosphate pesticides or nerve agents—acetylcholine accumulates, causing a cholinergic crisis with symptoms like salivation, lacrimation, bronchospasm, bradycardia, and muscle weakness. Measuring a drop in acetylcholinesterase activity helps confirm exposure and assess severity, guiding urgent treatment.

Amylase and lipase are pancreatic enzymes; their clinical relevance is mainly in elevations seen with pancreatitis, not decreases. Creatine kinase (CK) reflects muscle injury when elevated; decreases aren’t used diagnostically.