Question

According to the induced-fit theory of enzyme activity
A) Substrate induced conformational change in enzyme
B) Substrate changes its shape after binding
C) Conformational change takes place in substrate
D) There is no conformational change in enzyme

Answer 1

Hint: Koshland proposed the induced fit theory in 1958. Enzymes are called a biological catalyst; they reduce activation energy allowing the reactions to proceed in the desired direction. Enzyme activity is referred to as a measure of the number of active enzymes present. The SI unit is the katal. An active site is referred to as part of an enzyme where substrate molecules get attached. When the substrate is attached to the active site it is changed into the product.

Complete answer:
- Three different enzyme models represent enzyme-substrate binding: the lock-and-key model, the induced fit model, and the transition-state model.
- Induced fit is the most preferred because it was a development of the lock and key mechanism as it suggests that the enzyme's active site changes slightly so that the substrate can fit.
- According to the induced-fit theory of enzyme, the structure of the active site of the enzyme molds itself according to the shape and size of the substrate.
- According to the induced-fit model, both enzyme and the substrate undergo dynamic conformational changes upon binding. The enzyme distorts the substrate into its transition state, hence increasing the rate of the reaction.
- This model allows the binding of a substrate or some other molecule to an enzyme that causes a change in the shape of the enzyme to enhance or inhibit the activity of the enzyme.
- The substrate approaches the enzyme surface and induces a change in its shape that results in the correct alignment of the catalytic groups
- The catalytic groups at the active site of the enzyme react with the substrate to form products.
- The products separate from the enzyme surface, and the enzyme can repeat the sequence.
- In noncompetitive inhibition where compound inhibits the reaction of an enzyme but does not prevent the binding of the substrate.
- In such cases, the inhibitor compound attracts the binding group so that the catalytic group is too far away from the substrate to react.
- The site at which the inhibitor binds to the enzyme is not the active site and is called an allosteric site. The inhibitor changes the shape of the active site to prevent catalysis without preventing the binding of the substrate.
- Allosteric sites are regulatory sites that can activate or inhibit enzymatic activity by influencing the shape of the enzyme.
- In enzyme carboxypeptidase, the binding of the substrate causes a tyrosine molecule at the active site to move by as much as 15 angstroms.
- Hence, the induced fit theory of enzyme activity substrate induced conformational change in enzyme.

So, the correct answer is option (A).

Note: An enzyme and a substrate are close to each other. The substrate is referred to as the biological molecule that the enzyme will work on. The enzyme binds with the substrate at a special area called the active site. The alteration taking place at the active site is known as an induced fit. Enzyme activity can be affected by factors, such as temperature, pH, and concentration. They require optimal conditions.