Non-competitive inhibitors bind away from the active site

Steps:

• Recall enzyme inhibition types: competitive inhibitors bind the active site, blocking substrate; non-competitive bind elsewhere, altering enzyme function.
• Identify reversible: inhibitor binds non-covalently, can dissociate.
• Match to non-competitive: attachment at allosteric site (not active site) reduces enzyme activity without competing with substrate.
• Eliminate options not fitting reversible non-competitive definition.

Why B is correct:

• Non-competitive inhibitors bind to an allosteric site other than the active site, changing enzyme conformation to reduce activity while allowing substrate binding (per enzyme kinetics definition).

Why the others are wrong:

• A describes competitive inhibition, which blocks the active site directly.
• C suggests mixed inhibition, where binding can occur at both sites simultaneously.
• D fits uncompetitive inhibition, binding either free enzyme or enzyme-substrate complex variably.

Final answer: B