Enzyme Inhibitors

• Graph 1

  A) No Inhibitor

  B) Non-Competitive Inhibitor

  C) Non-Competitive

  
• Graph 2

  A) Competitive Inhibitor

  B) No Inhibitor

  C) Competitive

  
• Enzyme Inhibitors

  • Reduce enzyme activity by interfering with active site
  • End-product Inhibition:
  • Sometimes desirable to regulate/control metabolic pathways
  • End product binds to allosteric site to act as reversible non-competitive inhibitor
  • Reversible Inhibitors:
  • Use weaker hydrogen or ionic bonds
  • Non-reversible Inhibitors:
  • Strong covalent bonds
• Enzyme Inhibitor types

  • Competitive Inhibitors
  • Similar shape to substrate
  • Occupy active site for a short time (reversible)
  • No reaction takes place when bind
  • Effect depends upon inhibitor and substrate concentrations
  • If substrate concentration increases, inhibition reduces
  • Non-Competitive Inhibitors
  • Dissimilar shape to substrate
  • Don’t bind to active site, but to allosteric site
  • Cause tertiary structure (and active site) to change shape
  • Substrate can no longer bind
• Poisons and Drugs affecting Enzyme Activity

  • Potassium Cyanide:
  • Non-competitive inhibitor of respiratory enzyme cytochrome oxidase (in mitochondria)
  • Aerobic respiration can’t produce ATP
  • Exposure causes unconsciousness, then death
  • Ethylene Glycol:
  • Antifreeze Component in car engines
  • Poisonous if broken by alcohol dehydrogenase in liver (makes oxalic acid)
  • It is non-toxic, so excreted
  • Competitive inhibitor for alcohol
  • Treatment: massive alcohol dose
  • Penicillin:
  • Antibiotic
  • Prevents bacterial cell reproduction
  • Inhibits enzyme required for bacterial cell wall synthesis