Introduction:
Enzymes are biocatalysts and are organic in nature.
All enzymes are proteins in nature (except Ribozymes)
Factors affecting enzyme action.
Many factors affect enzyme activity, they are as follows,
Temperature.
Enzyme Concentration.
pH.
Substrate concentration.
Product concentration.
Activators and Inhibitors.
Water.
Temperature:
An enzyme's activity is greatest within a narrow temperature range.
The temperature at which an enzyme exhibits maximum activity is referred to as the optimum temperature.
The optimum temperature for most of the enzymes is between 25-35°C. Temperature above and below this range affects the enzyme activity.
High temperature above 50°C results in the destruction of enzymes by causing their denaturation, and very low temperature restores the enzymes in their inactive state.
Enzyme Concentration:
The rate of the enzymatic reaction increases with increasing enzyme concentration until it reaches a point known as the saturation point.
Above this limit, there is very little effect on enzyme activity.
pH:
Enzymes work at their optimum pH.
Increase or decrease in pH reduces the activity of enzymes.
Most of the intracellular enzymes function near-neutral pH except for many digestive enzymes that are active in different pH ranges.
Change in pH causes change in the structure of the enzyme, including its active site.
At extreme pH, denaturation of enzymes occurs.
Substrate concentration:
At the start, the rate of enzymatic reaction increases with the increase in substrate concentration.
In the beginning, the velocity of the reaction is high, but later it does not increase progressively with the increase in substrate concentration.
It happens because enzyme molecules get fully saturated, and no more active sites are left free to bind additional substrates.
In the graph below, the low value of Km (Michaelis-Menten constant) indicates a strong affinity between the enzyme and substrate.
On the other hand, a high value of Km shows a weak affinity between the enzyme and the substrate.
Product concentration:
The accumulation of the products of reaction causes decreases in the activity of enzymes.
When products accumulate, they combine with the active site of enzymes, thus forming a loose complex that inhibits the activity of enzymes.
Activators and Inhibitors:
Some chemical substances or molecules increase the activity of enzymes such as cofactors, for example, manganese ion (Mn²⁺), etc.
These chemicals which increase the activity of enzymes are known as activators.
On the other hand, certain drugs or poisons inhibit the activity of enzymes e.g. heavy metal compounds, Allopurinol which is used in Gout.
Water:
Water is the place in which enzymatic reactions take place.
The presence of water increases the reaction rate, whereas the absence of water inhibits the enzyme activity.
Light:
Enzymes are sensitive to light.
The presence of light increases the reaction rate in some enzymes whereas the presence of harmful radiation such as UV rays and X-rays decomposes enzymes.
Commonly Asked Question.
What are Enzymes? Discuss various factors affecting enzyme activity.