Question

(a) How is mature insulin different from Proinsulin secreted by the pancreas in humans?
(b) Explain how human functional insulin is produced using rDNA technology.
(c) Why is the functional insulin produced considered better than the ones used earlier by diabetic patients.

Answer 1

Hint: Insulin is a peptide hormone produced by beta cells of the pancreatic islets it is considered to be the main anabolic hormone of the body. It is a hypoglycemic hormone that is used to decrease the glucose content of the blood.

Complete step-by-step answer: In mammals, including humans insulin is synthesized as a prohormone like a proenzyme the prohormones also need to be processed before it becomes a fully mature and functional hormone which contains an extra stretch called the C peptide. This C peptide is not present in mature insulin and is removed during maturation into insulin.
-Eli Lilly an American company prepared two DNA sequences corresponding to A and B chains of human insulin and introduced them in plasmids of E.coli to produce insulin chains and A and B were produced separately, extracted, and combined by creating disulfide bonds to form human insulin.
-Insulin used for diabetics was earlier extracted from the pancreas of slaughtered cattle and pigs. Insulin from animal sources, though, caused some patients to develop an allergy or other types of reaction due to the foreign protein. Due to the following reason insulin used nowadays is more useful than insulin used in earlier days for diabetic patients.

Additional information :
-Recombinant DNA technology involved several steps in specific sequence such as isolation of DNA, fragmentation of DNA by restriction endonuclease, isolation of the desired DNA fragment, ligation of the DNA fragment into a vector, transforming the recombinant DNA into the host, culturing the host cells in the medium at large scale and extraction of the desired product.

Note: The construction of the first recombinant DNA emerged from the possibility of linking a gene encoding antibiotic resistance with the native plasmid of Salmonella typhimurium.