Factors affecting enzyme activity

Introduction: 

• Enzyme activity can be affected by a variety of factors, such as temperature, pH, and concentration.
• Decrease in activation  energy leads to an increase in enzyme activity.
• Enzymes work best within specific temperature and pH ranges, and sub-optimal conditions can cause an enzyme to lose its ability to bind to a substrate.
• One  unit enzyme  activity  is  defined  as the  amount  causing  transformation  of 1.0  micro  mole  of  substrate  per  minute(Micromole / minute)  at  25o  C
• Temperature: Raising temperature generally speeds up a reaction, and lowering temperature slows down a reaction. However, extreme high temperatures can cause an enzyme to lose its shape (denature) and stop working.

1. Bell  shaped  curve  is  obtained  by  plotting temperature against  velocity  of reaction
2. The optimum  temperature  for  most  human  enzymes is  between  35  and  40⁰C.
3. The  temperature  coefiicient  (Q10)  is  the  factor  by which  the  rate  of  a biologic process increases  for  a 10’C increase  in  temperature.

• pH: Each enzyme has an optimum pH range. Changing the pH outside of this range will slow enzyme activity. Extreme pH values can cause enzymes to denature.

• Enzyme concentration: Increasing enzyme concentration will speed up the reaction, as long as there is substrate available to bind to. Once all of the substrate is bound, the reaction will no longer speed up, since there will be nothing for additional enzymes to bind to.      

• Substrate concentration: Increasing substrate concentration also increases the rate of reaction to a certain point. Once all of the enzymes have bound, any substrate increase will have no effect on the rate of reaction, as the available enzymes will be saturated and working at their maximum rate

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