Question

What are the physical and chemical properties of enzyme active sites. Use the enolase mechanism to illustrate as many of these as you can.

Answer 1

The active site is consists of amino acids from different residue of the primary structural sequence of proteins and it have three dimensional geometry. The activity of the enzyme active sites is due to the binding specificity of the different amino acids, but form the active site as a result of folding in creating the tertiary structure. This active site region is generally small compare to whole enzyme structure. Like a ligand-binding site, the majority of an enzyme exist primarily to serve as a framework to promotes the structure of the active site by providing correct orientation. The unique amino acids contained in an active site promote specific interactions that are necessary for proper binding and resulting catalysis.

The characteristics of an enzymes are generated from the amino acid sequence which basically measures the structure of the active site and hence the specificity of the enzyme. The interaction force between enzyme and substrate may originated from the physical and chemical nature of both. Electrostatic interaction between oppositely charged groups may play crucial role. Such electrostatic interaction may occur with groups that are completely positively or negatively charged or with groups that have partial charge .The attractive forces between substrate and enzyme may originated from the hydrophobic interaction and the substrate are forced together in the same way as oildroplets tend to coalesce in water.

Structural modification near the active site affect the enzyme’s activity, because these amino acids are intimately involved in the fit and attraction of the substrate to the enzyme surface. The characteristics of the amino acids near the active site determine whether or not a substrate molecule will fit into the site. For a bulky substrate fit may be unusual into the active site and thus cannot react with the enzyme. In a similar manner, a molecules which doesnot have attractive force might not be bound to the enzyme. On the other side, if a molecule contain bulky group at a position in such a way that it does not interfere with the binding of the molecule to the enzyme, active site is able to serve as a substrate for the enzyme. This phenomenon of fit between substrate and enzyme, called the key–lock mechanism