forms of enzyme inhibition

chem further

reversible, competitive inhibitors

• structural analogues of the substrate

• competes with the substrate for the active site of the enzyme

• doesn’t affect

  • inhibitive effect can be outcompeted by increasing the substrate concentration
  • i.e. the substrate will ultimately occupy all binding sites
  • enzyme-catalysed reaction in the presence of a competitive inhibitor remains unchanged from normal

• affects

  • a higher substrate concentration is required to reach , to overcome inhibitory effects of the competitor

reversible, non-competitive inhibition

• generally structurally unrelated to the substrate

• binds to an allosteric site

• theoretically, the substrate and the inhibitor can bind to the enzyme at the same time

• the inhibitor distorts the active sites, reducing the effectiveness of the complex

  • alters the conformation of their catalytic residues

• doesn’t affect

  • effect of this inhibitor cannot be reversed by increasing substrate concentration
  • enzyme-substrate affinity unchanged as both and can bind at the same time

• affects

  • reduction due to reduced effectiveness of complex

uncompetitive inhibition

• do not react with the free enzyme
• combines with the complex to slow down or prevent formation of product
• affects
• affects

irreversible / suicide inhibition

• reacts covalently with an amino acid side chain on the enzyme to form a stable complex that is permanently inactivated

• some attach to active sites, known as “mechanism based suicide substrates”

• reduces amount of active enzyme, kinetic effects similar to noncompetitive inhibitors

• may affect

  • measures the affinity of the enzyme to the substrate, but it is based on the active enzyme present
  • if the inhibitor disallows

• affects

  • enzyme’s catalytic capacity is permanently reduced so is reduced