INSULIN is a peptide hormone produced by beta cells in the pancreas.
It plays a crucial role in regulating blood glucose levels by facilitating the uptake of glucose into cells, particularly in liver, fat, and muscle tissues.
Insulin helps in the metabolism of carbohydrates, fats, and proteins. When blood sugar levels rise, such as after eating, the pancreas releases insulin to help cells absorb glucose, reducing blood sugar levels to a normal range.
In people with diabetes, the function or production of insulin is impaired, necessitating external insulin administration for blood sugar regulation.
Synthesis of Insulin:
Initiation with Preproinsulin:
The synthesis of insulin begins with the formation of an inactive precursor molecule known as "preproinsulin," consisting of 110 amino acids.
Production in the Rough Endoplasmic Reticulum:
Preproinsulin is synthesized within the rough endoplasmic reticulum.
Storage and Transformation into Proinsulin:
The synthesized preproinsulin is then stored in the Golgi apparatus, where it is transformed into proinsulin, an inactive form.
Folding and Formation of Disulfide Bonds:
Proinsulin undergoes folding, resulting in the formation of three disulfide bonds. These bonds connect the two ends of the protein, known as the "A-chain" and the "B-chain."
Packaging in Secretory Vesicles:
The folded proinsulin is subsequently packed into specialized secretory vesicles after it passes through the Golgi apparatus.
Cleavage of Proinsulin:
Within these vesicles, enzymes Proprotein Convertase 1/3 and Proprotein Convertase 2 act on proinsulin. They cleave the "C-peptide," which is the central part of the molecule.
Final Processing by Carboxypeptidase E:
Carboxypeptidase E further processes proinsulin by removing two pairs of amino acids from the ends of the protein.
Formation of Active Insulin:
This processing yields active insulin, which consists of the A and B chains connected by two disulfide bonds.
Characteristics of Active Insulin:
The active form of insulin features two chains: Chain A with 21 amino acids and Chain B with 30 amino acids. These chains are linked by two disulfide bonds.
Secretion into the Bloodstream:
Following its synthesis, active insulin is secreted into the bloodstream, where it performs its physiological roles.
Here is the modified, colorful flowchart depicting the Synthesis of Insulin:
This process highlights the intricate steps involved in the synthesis and preparation of insulin, essential for regulating key metabolic processes in the body.
