The document discusses insulin, describing its structure as a peptide hormone composed of two chains of amino acids linked by disulfide bridges that is produced in the beta cells of the pancreas. It explains insulin's role in regulating blood glucose levels through mechanisms like stimulating glucose uptake into cells and promoting the synthesis of enzymes involved in glucose metabolism. The summary also outlines insulin's synthesis, storage, and the factors that stimulate and inhibit its secretion.

1. BIOCHEMISTRY GROUP NO .02
• QN. Describe about the insulin based on,
• Tell about the insulin and storage
• Location of insulin ,storage and size
• Genes make the insulin
• Amino acid made the insulin ,sequence and structure
• Insulin is a multi or mono subunit
• Domains of insulin
• Synthesis and regulation of the insulin
• Metabolic effect of insulin
• Functions of the insulin

2. Tell about the insulin and storage
• Insulin; Is a peptide hormone produced by beta cells of the pancreatic
islets encoded in humans by the INS gene
>Insulin is a globular protein stored in β- cell as zinc ion stabilized hexamer
Location and gene that make the insulin
>Insulin hormone is located in chromosome number eleven (11) at position
15.5 Size and structure
Insulin is a large protein consist of 51 amino acids in the two chains
namely chain A and B ,Where by chain A consist of 21 amino acids and
chain B consist of 30 amino acids.40-50 units are produced daily in human
body. The chain are linked by three disulfide bridges, two forming
interchain cystein at A7-B7 and A20-B19 and one forming an intrachain
cystein at A6-A11


4. Amino acid made the insulin sequence and
structure
• There are 16 amino acid contained in the insulin, which are
• -glycine, isoleucine ,valine ,glutamine ,glutamate, cystein ,threonine,
serine, leucine, tyrosine ,asparagines,
phenlalanine,histidine,prorine,arginine and lycine
•

5. Structure of Insulin
• It has two long amino acids chain or polypetide chains.The chains are
chain A with 21 amino acids and a chain B with 30 amino acids.Two
disulfide bridges (residues A7 to B7, and chain A20 to B19) covalently
connect the chains, and chain A contain an internal disulfide bridge
(residuesA6 to A11)
• DOES INSULIN A MULTI OR MONO SUBUNIT
• Insulinis a multi subunit wih the molecular weight 6000Da
constituents two amino chains linked by two disulfied bridge

6. Domains of insulin
• -Proteins of insulin super-family are synthesized as prepro-proteins consist of four
domains which are (pre,B,C,A)
• -Insulin is produced by the β-cell of islet of langerhans of pancrease.
The synthesis of insulin involve two precursors namely, preproinsulin with 180
amino acid and pro insulin consist 86 amino acid
• -Preproinsulin and proinsulin undergoes proteolytic degradation
• *At first stage,preproinsulin undergoes proteolytic degradation to remove signal
sequence called predomain.The process takes place in the endoplasmic
reticulum, The remain part is called proinsulin consist of 86 amino acids
• *Proinsulin also undergoes proteolytic degradation to remove C peptide chain
(which is C-domain).The process takes place in agolgi apparatus toform insulin
• *Insulin is formed by domain A and B linked by disulfide bond

8. Synthesis and regulation of insulin
Synthesis of insulin
>insulin produced by better cell of islets langerhans of the pancrease. The gene for
this protein synthesis is located on chromosome 11.the synthesis of insulin involve
precursors ,namely preproinsulin with 108 amino acids and proinsulin with 86
amino acids
Regulation of insulin secretion
>factors stimulating insulin secretion
*glucose,the effect is more predominant when glucose is administered orally,a rise
of blood glucose level is a signal for insulin secretion
*Amino acid,after ingestion of protein meal that cause transient rise in plasma
amino acids,arginine and leucine are potent stimulators of insulin release
*gastrointestinal hormone,enhance secretion of insulin the GIT hormone are
release after ingestion of foods

9. Factor inhibiting insulin secretion
• Epinephrine is the most potent inhibitor of insulin release.Emergence of
situations like stress extreme exercise and trauma , the nervous system stimulate
adrenal medulla to release epinephrine
• Metabolic effects of the insulin
>Mechanism of insulin action
• -There are three mechanism of insulin action
• (1) Insulin receptor mediated signal transduction
• -It is tetramer consist of 4 subunit of two types and designated as α2β2.The
subunit are in the glycocylated form .they are hold together by disulfide linkage
• -the α subunit is extracellular and it contain insulin binding site
• -The β-subunit is a transmembrane protein which is activated by insulin ulin

10. - Signal transduction
• -When insulin hormone bind ti the receptor cause conformational
change induced in the α-subunit of insulin receptor , this result in the
generation of signals which are transduced to subunits
• -This effect of insulin binding activate the tyrosine kinase causing
autophosphorylation of tyrosine residue on β-subunit also tyrosine
kinase phosphorylate insulin receptor IRS
• -IRS inturn promote the activation of other protein kinases and
phosphate

12. 2) Insulin mediated glucose transport
• *The binding of insulin to insulin receptors signals , the translocation of
vesicles containing glucose transporter from intracellular pool to the
membrane
• *The vesicle fuse with the membrane recruiting the glucose transporter
• *The glucose transporters are responsible for insulin mediated uptake of
glucose by the cells
• *As insulin level falls, the glucose transporters move away from the
membrane to the intracellular pool for storage acid recycle
•
•

14. (3) insulin mediated enzyme synthesis
• Insulin promote the synthesis of enzyme such as glucokinase ,
phosphofructokinase and pyruvate kinase ;This is brought about by
increased transcription (mRNA synthesis) followed by translation
•
• Functions of insulin
• insulin,maintain normal blood glucose level by facilitating cellulal
glucose uptake ,regulating carbohydrate lipid and protein metabolism
and promoting cell division and growth