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Activity Recovered in Denaturing/Renaturing Types of Insulin

Insulin consists of two peptide chains, a shorter A-chain and a longer B-chain. The two chains are held together with disulfide bonds. Invivo, insulin is processed from a single polypeptide chain called proinsulin by specific protease. Processing involves removal of the C-chain from proinsulin as indicated.

A denaturation/renaturation experiment, similar to the one carried out by Anfinsen on ribonuclease, was performed. In contrast to his results, less than 10% activity was recovered upon removal of 2-Mercapoethanol and Urea. When the experiment was repeated on proinsulin , full activity was restored.

Please explain why this took place. A diagram is attached.


Solution Preview

In Anfinsen's original experiment, he denatured ribonuclease with 8M urea (this is a dissociating solvent and breaks all weak bonds). 2-mercaptoethanol is a reducing agent and reduces disulphide bridges to SH groups (sulphydryl), thus breaking them. This converts the enzyme to a random ...

Solution Summary

The solution provides a few paragraphs' written explanation as to the results of a denaturation/renaturation experiment similar to that performed by Anfinsen on ribonuclease which were substantially different than expected.