An enzyme exhibits sigmoidal kinetics in its velocity-substrate concentration (v vs [S]) curve with a Hill coefficient (n) of 3.2. A drug that stabilises the T (tense, low-affinity) state of this enzyme would act as:
- A Heterotropic allosteric activator
- B Competitive inhibitor
- C Homotropic allosteric inhibitor ✓
- D Uncompetitive inhibitor
Explanation
The sigmoidal kinetics and Hill coefficient > 1 indicate positive cooperativity in an allosteric enzyme with multiple substrate-binding subunits (the substrate itself is the effector — homotropic). Stabilising the T (low-affinity) state raises the apparent S0.5 (substrate concentration for half-maximal activity), shifting the sigmoid curve rightward — this is homotropic allosteric inhibition. Competitive inhibitors require a discrete active-site binding. Heterotropic effectors are non-substrate molecules. An n of 3.2 suggests at least 4 subunits with highly cooperative binding.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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