Enzyme, a substance made up of large protein molecules, acts as a catalyst to speed up the chemical reactions without getting consumed and lower the activation energy required to get the reaction started. Enzyme activity affected by a variety of factors follows are of some important kinds.
Enzyme Concentration: Enzyme concentration, [E] is directly proportional to the rate of reaction (V), that means as the enzyme concentration is increased the rate of reaction increases.
Substrate Concentration: In enzyme catalytic reactions, two steps of reactions are considered, first substrates bind with enzymes to form enzyme-substrate complexes, ES and second formation of products.
S+E---------ES complex------ Products.
At initial stage of reaction, the velocity of reaction, Vo is directly proportional to substrate concentration, but decreases gradually and reaches its maximum at the point of enzymes becomes saturated with substrates. This point of saturation is called maximum velocity, Vmax and rate of reaction can not be further accelerated with increasing substrate concentration, [S] as all the enzymes are occupied with substrates. Substrate concentration at half of maximum velocity is called Michaelis-Menten constant (Km) and it is considered as the signature of an enzyme because it is specific for each enzyme.
Product Concentration: The products are here the substances produce in reactions and formed at the second stage of reaction. More product formation increases the products concentration, [P] and decreases the velocity of reaction.
Temperature: At very low temperature the enzyme activity is very low or zero. With the increase of temperature, the enzyme activity rises, reaching a certain point after due to denaturation of enzyme by temperature and even goes to zero on destruction of enzyme by high temperature. Therefore, there is an optimum temperature for each enzyme at which the activity becomes peak.
pH: Each enzyme has a certain pH point needed to become activated and most of the enzymes are specific to a particular pH. Therefore, each enzyme has an optimum pH where the velocity of reaction is maximum.
Apart from this water, enzyme inhibitors, duration of time also play an important role in enzyme activity.