Enzyme Kinetics

• Enzyme-catalysed reaction rate


  • Can be calculated and plotted according to the time taken for the reaction to proceed
  • Can be measured according to either the amount of product formed or the amount of substrate consumed
  • Reaction rate is the inverse of time taken, meaning that the reaction rate is higher when less time is taken (and vice versa)
• Rate of reaction


  Calculated according to the formula: Rate of reaction (s–1) = 1 / time taken (s)
• Factors which can influence the rate of an enzyme-catalysed reaction


  • Temperature
  • pH
  • Substrate concentration
• Competitive inhibitors


  • Bind directly to the active site and hence exist in direct competition with the substrate
  • Increasing substrate levels will increase the likelihood of the enzyme colliding with the substrate instead of the inhibitor
  • The maximum rate of enzyme activity (Vmax) can still be achieved, although it requires a higher substrate concentration
• Non-competitive inhibitors


  • Bind to an allosteric site and hence do not exist in direct competition with the substrate
  • Increasing substrate concentrations will not effect the level of inhibition caused by the non-competitive inhibitor
  • The maximum rate of enzyme activity (Vmax) is therefore reduced
• Types of inhibition


  • Competitive
  • Non-competitive
• Competitive and non-competitive inhibitors


  Effect the kinetics of an enzyme-catalysed reaction in different ways
• Both competitive and non-competitive inhibitors reduce the rate of reaction by limiting the amount of uninhibited enzyme available for reaction