in the synthesis of insulin in the lab ..

 

the e coli is the ideal choice for amplifying the insulin !!!

 

However the synthesis of Factor VII for haemophilics is not inserted to a bacterial cell but a MAMMALIAN !??!?!

 

i am briefed with the answer :

 

mammalian cells have Golgi apparatus for modification of polypeptides after the traslation of factor VII

 

 

my question is why insulin is synthesised using e.coli but Factor VII is in mammalian cells !??????

 

is it mean that insulin need no modification after translation ????

In principle yes. However the complete insulin consists of two gene products. The A and B chain have to make disulfide bonds in order to get to the correct quartiary structure.

On a different point, I think nowadays yeast cells are used as hosts as they can easily be made to secrete active insulin...

In principle yes. However the complete insulin consists of two gene products. The A and B chain have to make disulfide bonds in order to get to the correct quartiary structure.

On a different point' date=' I think nowadays yeast cells are used as hosts as they can easily be made to secrete active insulin...[/quote']

 

 

That is incorrect. It consists of one gene product coding for proinsulin that contains both the A and B chain linked by a spacer region (peptide C). proinsulin folds; disulfide bonds are created and the spacer region is cut from between the A and B chain leaving insulin.

 

This spacer region is necessary to ensure proper formation of disulfide bridges.

 

I believe that prodution in bacteria is for the proinsulin afterwards it is purified and then an invitro maturation technique is used.

 

alternativley as stated a yeast based fermentation can be setup to secrete active insulin.

is there any other clarification form others

 

????

Yeah I think what was said is right. A big advantage of yeast is the secretion part, as this reduces the amount of purification necessary and also reduces the chances of contamination. Diabetics obviously don't want to be injection E. coli cell contents into themselves.

Also, factor VII needs to be glycosylated (sugars linked to it), among other things, in order to be active. Therefore, mammalian cells are the expression systems of choice since the glycosylation signals will be more likely to be recognized.

http://en.wikipedia.org/wiki/Insulin

I stand corrected. I only had memorized that it contained two chains and I assumed that it was the results of two gene products.

However, if I recall correctly the first hetereologous expressions of insulin was done by expressing both chains seperately and then combining them chemically (hence my errror).

haemophylics need factor VIII i think not VII

 

large scale insulin production is produced in animal milk, i forget which one