Biological activity of protein

Biological activity can be defined as “the capacity of a specific molecular entity to achieve a defined biological effect” on a target. It is measured in terms of potency or the concentration of the molecular entity needed to produce the effect.

Biological activity of proteins is presentence of various protein functions. A protein with biological activity is called an active protein, namely, an active protein has biological activity.

The biological properties of a protein molecule depend on its physical interaction with other molecules. Thus, antibodies attach to viruses or bacteria to mark them for destruction, the enzyme hexokinase binds glucose and ATP so as to catalyze a reaction between them, actin molecules bind to each other to assemble into actin filaments, and so on. Indeed, all proteins stick, or bind, to other molecules.

Proteins in aqueous solutions, swell and enclose water. Protein solutions are colloidal emulsoids or micelles, because they are charged, and each molecule has an envelope of water around it. Protein denaturation occurs when a polypeptide loses its higher level of structure, and often results in loss of biological activity.

Milk is an excellent source of well-balanced nutrients and also exhibits a range of biological activities that influence digestion, metabolic responses to absorbed nutrients, growth and development of specific organs, and resistance to disease.

Milk protein is comprised of about 80% caseins and 20% whey proteins. These biological activities are mainly due to the peptides and proteins in milk. However, some of the biological activity of milk protein components is latent, and is released only upon proteolytic action.
Biological activity of protein