What are the Factors that Affect the Enzymatic Activity?

Several factors affect the rate of an enzyme catalyzed reaction. Among these are enzyme concentration, substrate concentration, temperature and pH. Besides, some molecules (activators) increase enzyme activity, while others (inhibitors) retard enzymatic activity.

Enzyme concentration: The reaction rate of an enzyme catalyzed reaction depends upon its own concentration. The completion time of the reaction is directly proportional to the enzyme concentration if the substrate concentration is fixed.

Substrate concentration: It is experimentally shown that if the enzyme concentration is fixed and the substrate concentration is gradually increased, the reaction velocity increases until it reaches a maximum. After this point, any more increase in the substrate concentration will not increase the velocity.

Temperature: Like most chemical reactions, the rate of an enzyme catalyzed reaction increases as the temperature is increased. A 10° C rise in the temperature will increase the activity of most enzymes by 50-100%. Variation in the reaction temperature, as small as 1 -2° C, may introduce a 10-20% increase in the reaction rate.

Most enzymes are adversely affected by a temperature above 40° C. They are rapidly denatured, i.e. lose catalytic activities. Enzymes lose their activity at extremely low temperatures as well. This may account for storing enzymes at 5° C or below without affecting the enzymatic activity permanently.

PH: Enzymes are affected by changes in the pH. The most favourable pH, at which an enzyme exhibits its maximum activity, is known as the optimum pH for the enzyme. Extremely high or low pH values generally result in complete loss of enzymatic activity. The optimum pH value varies greatly from enzyme to enzyme.

Inhibitors and activators: Many molecules affect the rates of enzyme catalyzed reactions. Some molecules bind to the enzyme or the substrate or the enzyme-substrate complex and lower the reaction rate. These are known as inhibitor molecules. Similarly, some bind to the enzyme molecule and consequently increase the reaction rate. These are known as activator molecules.