2' Factors affecting enzymatic activity

1
2. Factors affecting enzymatic activity

• Temperature
• temperature coefficient, Q10
• Rate of reaction at (x 10) oC
• Rate of reaction at x oC
• From 0 40oC enzymatic reaction is doubled for
  every rise of 10 oC
• ? Heat increases molecular motion ? reactants
  move more quickly ? chances of their bumping into
  each other are increased

2

• Optimum temperature temperature that promotes
  maximum activity
• gt optimum temperature ? rate of reaction
• If temperature is too low enzymes are
  inactivated

3

• pH
• Optimum pH pH that promotes maximum activity
• When the pH is above or below this value, the
  rate of enzymatic activity decreases

• Changes in pH ? alter the ionic charge of the
  acidic and basic groups that help to maintain the
  specific shape of the enzyme ? structure of
  enzyme changes (i.e. denatured)

4

• Enzyme and substrate concentration
• Rate of reaction is proportional to the enzyme /
  substrate concentration
• Increase enzymes / substrate concentration ?
  increases the chance for the formation of
  enzyme-substrate complex ? probability for a
  reaction to occur is higher

5

• Co-factors
• Non-protein components for their efficient
  activity
• 3 types
• Inorganic ions
• Prosthetic groups e.g. FAD and Haem groups
• Coenzymes e.g. NAD, ATP and coenzyme A

6

• Enzyme inhibition
• Enzyme inhibitors small molecules that have the
  ability to reduce the rate of an
  enzyme-controlled reaction
• 2 types
• Reversible inhibition can be minimized by
  increasing the concentration of substrate
• Irreversible inhibition combine with the enzymes
  permanently and once they combine, the enzyme is
  no longer effective

7

• End-product inhibition
• When the product of a metabolic pathway begins to
  accumulate, it may act as an inhibitor on the
  enzyme
• Acts as a negative feedback mechanism
• Serves to control the metabolic activity.