Botulinum toxin produces flaccid paralysis by which molecular mechanism?

• A Blocking acetylcholine synthesis by inhibiting choline acetyltransferase
• B Blocking uptake of acetylcholine into synaptic vesicles
• C Irreversible inhibition of acetylcholinesterase at the motor end plate
• D Proteolytic cleavage of SNARE proteins required for vesicle fusion with the presynaptic membrane ✓

Explanation

Botulinum toxin is a zinc dependent endopeptidase that cleaves SNARE proteins such as SNAP-25, synaptobrevin and syntaxin, preventing docking and fusion of acetylcholine vesicles with the presynaptic terminal membrane. Acetylcholine synthesis and vesicular uptake are unaffected, and cholinesterase is not inhibited. Hemicholinium blocks choline uptake and vesamicol blocks vesicular storage, so those are distinct mechanisms tested separately.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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