A globular protein is one of a common type of protein.
They are one of three types of protein. The others are fibrous and membrane proteins.
Their structure is a result of protein folding. They are made of polypeptide chains folded into a compact sphere shape.
They are soluble in water because of the hydrophilic ('water-loving') side chains that project from the outside of the molecules. They play an important role in metabolic reactions.
Unlike proteins which only have a structural function, globular proteins can act as:
- Enzymes, by catalyzing organic reactions taking place in the organism in mild conditions and with a great specificity. Different esterases fulfill this role.
- Messengers, by transmitting messages to regulate biological processes. This function is done by hormones, i.e. insulin etc.
- Transporters of other molecules through membranes
- Stocks of amino acids.
- Regulation of other molecules is also done by globular proteins rather than fibrous proteins.
- Structural proteins, e.g., actin and tubulin, which are globular and soluble as monomers, but polymerize to form long, stiff fibers.
Globular proteins include myoglobin and hemoglobin.
