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What is A drug that binds to receptor at a site distinct from the active site and alters the affinity of the receptor for the endogenous ligand is a: and explain in detail?
Ref. KDT. Page. 59
Competitive (equilibrium type –Allosteric modulator)

The drug being structurally similar competes with the normal substrate for the catalytic binding site of the enzyme
They increase the kM but the Vmax remains unchanged

Examples:

Physostigmine and neostigmine compete with acetylcholine for cholinesterase.
Sulfonamides compete with P ABA for bacterial folate synthetase.  
Moclobemide competes with catecholamines for monoamine oxidase-A (MAO-A).  
Captopril competes with angiotensin 1 for angiotensin converting enzyme (ACE).