Not a feature of competitive inhibition?
Inhibitor and substrate can bind simultaneously to same enzyme molecule
Inhibitor is structural analogue of substrate
Km increases
Vmax unaffected
Ans. a (Inhibitor and substrate can bind simultaneously to same enzyme molecule) (Ref. Harper 27th/Ch. 8)In noncompetitive inhibition, binding of the inhibitor does not affect binding of substrate. Formation of both El and EIS complexes is therefore possible. However, while the enzyme-inhibitor complex can still bind substrate, its efficiency at transforming substrate to product, reflected by Vmax, is decreased. Noncompetitive inhibitors bind enzymes at sites distinct from the substrate-binding site and generally bear little or no structural resemblance to the substrate.The effects of competitive inhibitors, which typically resemble substrates, are overcome by raising the con- centration of the substrate. Noncompetitive inhibitors lower Vmax but do not affect Km. Competitive Inhibitor reversibleCompetitive Inhibitors, irreversible Noncompetitive inhibitorsResemble substrateYesYesNoOvercome by | YesNoNoBind active siteYesYesNoEffect on VmaxUnchanged||Effect on Km|UnchangedUnchangedPharmacodynamics| potency| efficacy| efficacy# The lower the Km, the higher the affinity.Competitive inhibition# Vmax constant and Km increases with increasing inhibitor concentration.# Competitive inhibitors are analogues to the substrate chemically.# They bind at active site of enzyme and compete with substrate.# It is reversible; high substrate concentration can overcome it.HINT: Competitive inhibitors cross each other competitively, while noncompetitive inhibitors do not.
Enzymes