Active sites of the enzyme is that point where substrate molecule bind for the chemical reaction. It is generally found on the surface of enzyme and in some enzyme it is a “Pit” like structure The active site is a three-dimensional cleft formed by groups that come from different parts of the amino acid sequence The active site takes up a relatively small part of the total volume of an enzyme Active sites are clefts or crevices Substrates are bound to enzymes by multiple weak attractions. The specificity of binding depends on the precisely defined arrangement of atoms in an active site.