Index >> Enzymes,Isozymes and Coenzymes >> Active Site of Enzymes

Active Site of Enzymes -
An enzyme has a distinct cavity or cleft in which the substrate is bound.

The cleft contains an active centre in which the amino acids are grouped together in such a way as to enable them to combine with the substrate .

The reactive amino acids may lie widely separated in the polypeptide chain. The chain, however, undergoes folding in such a manner that the reactive amino acids come together in the active site.

It is believed that when the substrate molecule binds to the active site, its parts are held together in such a way as to cause distortion of the chemical bonds, i.e. the bonds are weakened.

Another way in which the reactive site is believed to speed up a, reaction is by excluding water molecules of the solvent from the site of reaction.

The tight fit of the substrate in the active site of the enzyme molecule does not permit water molecules at the site of reaction.

It is known that in the case of certain compounds exclusion of water molecules greatly affects the rate of reaction. Enzyme action:

There is a very close structural relationship between the molecular surface of an enzyme and its substrates. Enzymes are protein molecules with definite surface geometry.

The functional groups of the enzyme are exactly complementary to those of the substrate.