Enzyme Inhibition

• Enzyme inhibitor


  A molecule that disrupts the normal reaction pathway between an enzyme and a substrate
• Types of enzyme inhibition

  • Competitive
  • Non-competitive
• Normal enzyme reaction

  1. Substrate binds to enzyme (via active site) to form enzyme-substrate complex

  2. Active site undergoes conformational change to optimally interact with substrate (induced fit)

  3. Substrate is converted into product at an accelerated rate
• Competitive inhibition


  Inhibitor molecule binds to the enzyme's active site, blocking substrate binding
• Non-competitive inhibition

  Inhibitor molecule binds to a site other than the active site (allosteric site), causing a conformational change that prevents substrate binding
• Enzyme inhibitor uses


  • Medicine (to treat disease)
  • Agriculture (as pesticides)
• Competitive inhibitor example


  • Relenza (neuraminidase inhibitor to treat influenza)
• Normal infection

  Virions released from infected cells when viral enzyme neuraminidase cleaves docking protein
• Treatment with Relenza


  Relenza competitively binds to neuraminidase active site, preventing cleavage of docking protein, virions not released
• Non-competitive inhibitor example

  • Cyanide (binds to allosteric site on cytochrome oxidase, preventing electron transport chain function and ATP production)
• Normal electron transport chain function

  Electrons passed to final acceptor (oxygen)
• Treatment with cyanide


  Cyanide binds to allosteric site on cytochrome oxidase, preventing electron transport chain function and ATP production