Question

Formation of enzyme-substrate complex (ES) is the first step in catalysed reactions. Describe the other steps till the formation of product.

Answer 1

An enzyme catalyses a reaction, which means it hastens the rate of reaction. Thus, if under normal circumstances a particular number of units of a product is formed; one can get many times more units at the same time when the reaction is enzyme-mediated.

An enzyme-mediated reaction can be broken into three main steps, which are as follows:

1. Formation of the enzyme-substrate complex (ES)
2. Transient Stage
3. Formation of Product

In the first step. the enzyme binds to the substrate at the ‘active site’. This results in the formation of an enzyme-substrate complex.

Transient Phase: This is the altered structure state of the substrate. This is the unstable stage. Had there been no enzyme, the required activation energy would have been much higher. But because of the presence of enzymes. the reaction takes place with a less amount of energy.

Formation of Product: Once the transient phase is over, the final product is formed. With this, the potential energy of the system also comes down drastically. This can be shown by the following graph. Once the product is formed, the enzyme becomes free to bind with another substrate.