Brent Cornell

    
Various factors may affect the activity of enzymes, by either affecting the frequency of enzyme-substrate collisions or by affecting the capacity for the enzyme and substrate to interact (e.g. denaturation)

• Temperature, pH and substrate concentration will all influence the rate of activity of an enzyme

Temperature

• Low temperatures result in insufficient thermal energy for the activation of an enzyme-catalysed reaction to proceed
• Increasing the temperature will increase the speed and motion of both enzyme and substrate, resulting in higher enzyme activity
• This is because a higher kinetic energy will result in more frequent collisions between the enzymes and substrates
• At an optimal temperature (may vary for different enzymes), the rate of enzyme activity will be at its peak
• Higher temperatures will cause enzyme stability to decrease, as the thermal energy disrupts the enzyme’s hydrogen bonds
• This causes the enzyme (particularly the active site) to lose its shape, resulting in the loss of activity (denaturation)

The Effect of Temperature on Enzyme Activity

pH

• Changing the pH will alter the charge of the enzyme, which in turn will alter protein solubility and overall shape
• Changing the shape or charge of the active site will diminish its ability to bind the substrate, abrogating enzyme function
• Enzymes have an optimal pH (may differ between enzymes) and moving outside this range diminishes enzyme activity

The Effect of pH on Enzyme Activity

Substrate Concentration

• Increasing substrate concentration will increase the activity of a corresponding enzyme
• More substrates mean there is an increased chance of enzyme and substrate colliding and reacting within a given period
• After a certain point, the rate of activity will cease to rise regardless of any further increases in substrate levels
• This is because the environment is saturated with substrate and all enzymes are bound and reacting (V_max)

The Effect of Substrate Concentration on Enzyme Activity