Brent Cornell

    
The rate of an enzyme-catalysed reaction can be calculated and plotted according to the time taken for the reaction to proceed

• The time taken 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)

The rate of reaction can be calculated according to the following formula:

• Rate of reaction (s^–1) = 1 / time taken (s)

Factors which can influence the rate of an enzyme-catalysed reaction include temperature, pH and substrate concentration

Factors Affecting Enzyme Activity

    
Competitive and non-competitive inhibitors effect the kinetics of an enzyme-catalysed reaction in different ways:

• Both reduce the rate of reaction by limiting the amount of uninhibited enzyme available for reaction

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

Noncompetitive 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

The Effect of Inhibition on Enzyme Kinetics