Bioengeneering of Insulin Flashcards
What stabilizes the structure of Insulin?
Inter and intra-strand disulfide bonds connecting the A and B chains
3 A-B dimers form one Insulin hexamer
How is Insulin stored in the pancreas?
As an insulin hexamer bc it is more stable to chemical and physical degradation
Insulin receptors bind to the monomer
Why do Insulin monomers act faster?
-Insulin receptors react to monomers
-It takes some time for the hexamer to dissemble
-Monomers are ready to go but have a short halflife
What is a regular (short-acting) insulin?
HUMULIN R
made with recombinant DNA technology that assembles the same things pancreatic cells make -> closest mimic to natural insulin produced from the ß-cell
Why is Humulin R insulin absorbed relatively fast?
A mix of hexameric, dimeric, and monomeric - like natural Insulin
Initially, monomers bind to the receptors -> fast response
overtime dimers form -> Hexamer (makes it last for a couple of hours)
Which end and which chain controls the formation of hexamers?
-The formation is controlled by the C-terminus ends, more often the B-chain bc it is more available
-C-terminus must be left alone and stay available
-The hexamer formation is often around a kations
Where are bioengineered alterations installed?
At the C-terminal of B-chains, bc it is more accessible
What is a longer-acting Insulin?
Insulin NPH Neutral Protamine Hagedorn (made with human Insulin)
Hexamer forms around a katione:
Protamine a positively charged protein, and zinc (+2) are added to insulin to stabilize the hexameric structure in the mixture
(suspension - shaking will physically force the breakdown of the hexamers -> more monomers would increase the dosage unintentionally)
What is the characteristic of Protamine?
Protamine contains many Arginines -> Basic residue-rich proteins and thereby stabilizing the hexamer structure of insulin
What are the roles of Protamine and Zinc in INSULIN NPH?
-Protamine keeps the hexamers together
-Zinc stabilizes the formation
How does insulin behave in solution or when injected?
When hexamers are formed they are not soluble -> suspension is formed
They form monomers again when injected
What are the consequences of more hexamers?
-Slower onset (beginning of effect)
-longer peak
-last longer
What is one example of rapid-acting insulin?
Humalog: Insulin LisPro (switch of ProB28 on B-chain - Prolin and Lysin)
How does Prolin contribute to the rapid-acting characteristics of Insulin?
the cyclic structure of Prolin provides a steric hindrance to hexamer formation
-> faster acting, faster peak, shorter halflife
What is another example of rapid-acting insulin?
Aspart Insulin- NOVOLOG: ProB28 change to AspB28
-> another carboxylic acid charged AA (doesn’t help with hexamer formation -> it actually favors breakdown, bc of the repulsion with the A-chain -> causing ONLY monomers to form, acting very fast (minutes)
