QS Study

Insulin is a hormone that is significant for metabolism and deployment of energy from the ingested nutrients – especially glucose. It is a protein chain or peptide hormone. It helps keeps your blood sugar level from getting too high or too low.

Mechanism of action of the Insulin

  1. Insulin receptor:

The insulin receptor is a combination of four glycoprotein subunits held together by disulfide linkages. Two alpha (α) subunits that lie entirely outside the cells membrane and two beta (β) subunits that penetrate through the membrane, protruding into the cell cytoplasm.

  1. Binding of insulin with receptor:

Insulin binds with the alpha subunits on the outside of the cell.

  1. Autophosphorylation of beta subunits:

Because of the linkage with the beta subunits causes autophosphorylation of the portion of beta subunits protruding into the cell on tyrosine residues.

  1. Tyrosine kinase activity of beta subunits

Autophosphorylation makes the β subunits an activated enzyme; a local tyrosine kinase.

  1. Phosphorylation of other intracellular enzymes.

Tyrosine kinase causes phosphorylation of multiple other intracellular enzymes. The net effects are to activate some of these enzymes. These lead to many physiological functions.

Fig.: Mechanism of action of insulin.