All proteins in a living system possess definite configuration and biological activity. A protein found in a living system with definite configuration and biological activity is called native protein. In this state the protein possesses maximum hydrogen bonds.
A native protein may be coagulated and precipitated from aqueous solutions by heat, addition of acids, alkalies, salts or organic solvents miscible with water. The proteins in this state are said to denatured. During denaturation process, the soluble forms of proteins such as globular proteins often undergo coagulation or precipitation to give fibrous proteins which are in soluble in water. The coagulated proteins thus formed are called denatured proteins.
Therefore, a process that changes the physical and biological properties of the proteins without affecting the chemical composition of a protein is called denaturation.
Note:
- Chemically, denaturation does not change the primary structure but changes the secondary and tertiary structures of proteins.
- Denaturation of proteins can cause by changes in pH, temperature or by adding other denaturating agents.
- Denatured protein loses its biological activity.
- During denaturation, the protein molecule uncoils from an ordered and specific conformation into a more random conformation leading to precipitation. Thus, denaturation leads to increase in entropy.
- Denaturation may be reversible or irreversible.