Question

Which of this is not true for the active site of an enzyme?

(a) Active site is constituted by 3 to 4 amino-acids in a big protein structure

(b) Active site is mainly constituted by non-polar amino acids for catalysis to take place

(c) Water is generally included in the site

(d) Active site is a cleft formed by different amino-acids from different positions in an enzyme molecule

This question was posed to me in exam.

Query is from Enzyme Kinetics in section Enzyme Kinetics of Enzyme Technology

Answer 1

The correct answer is (c) Water is generally included in the site

For explanation I would say: Active site has the following features:

* It is a cleft formed by different amino-acids from different positions in an enzyme molecule.

* It is constituted by 3 to 4 amino-acids in a big protein structure.

* It is mainly constituted by non-polar amino-acids for catalysis to take place. Sometime polar may also be present. Water is excluded from the site unless it’s a reactant.

* The ES complex is a must to form products. So, appropriate substrate binding site is essential for any enzyme.

* The specificity of substrate binding is mediated by spatial arrangement of atoms in an enzyme’s substrate binding site as well as substrate.

Therefore, water is generally included in the site is not true for active site.