Question

What is it about protein enzymes that confers upon them their specificity?

Answer 1

Answer: Enzymes are proteins. Proteins are one of the most complex macromolecules with its three dimensional structure. Enzymes function by binding to the substrate molecule.

The binding of enzyme to the substrate is highly specific i.e. an enzyme specific towards a particular substrate will not be able to bind to another substrate. Thus enzyme catalysed reactions are highly specific.

Substrate binds to the enzyme at a particular site only which is known as the active site.

The binding of enzyme to the substrate is like lock and key where the enzyme functions like lock and the substrate is the key.

Lock and key hypothesis says that the enzyme substrate bind perfectly in one step but now we have an extension of this hypothesis that is induced fit model, according to this the initial binding between enzyme and substrate is weak but this weak binding initiates conformational changes to strengthen the binding.

Enzymes carry out the chemical reactions by binding to the substrate in optimal orientation so that the chemical reactions can occur.

As we know majority of the enzymes are proteins, the basic structure of a protein is a chain of amino acids i.e. a polypeptide and the properties of the amino acids is because of the R side chain. The R side chains of different amino acids exhibit different properties depending on the groups present on it and show different properties like they could be polar/non-polar, acidic/basic, positively charged/negatively charged etc.

The polypeptide when it undergoes conformational changes to form a specific protein, the R side chains of the various amino acids will be oriented such that it will create a unique chemical environment in the active site and that makes the active site specific towards particular substrate molecule.

Hence binding of enzyme and substrate molecule is highly specific