Q.Which cells of the Islets of Langerhans in the pancreas produce the peptide hormone insulin?

Insulin is a peptide hormone made by the beta-cells of the islets of Langerhans in the pancreas, essential for controlling blood sugar; people with diabetes mellitus cannot make enough of it. It was discovered by Sir Edward Sharpey-Schafer in 1916. To produce it by recombinant DNA technology, Hakura and co-workers (1977) chemically synthesised the DNA sequences for insulin's A and B chains and inserted them separately, next to a beta-galactosidase gene, into two different pBR322 plasmid vectors; the two recombinant plasmids were transformed separately into E. coli hosts, which produced a penicillinase + pre-pro-insulin fusion product, from which insulin was later released by treatment with trypsin. The overall design for this process is credited to Gilbert and Villa-Komaroff (1978). …