Recombinant bacterial plasmids have been constructed that contain complementary DNA prepared from rat islets of Langerhans messenger RNA. Three plasmids contain cloned sequences representing the complete coding region of rat proinsulin I, part of the preproinsulin I prepeptide, and the untranslated 3' terminal region of the mRNA. A fourth plasmid contains sequences derived from the A chain region of rat preproinsulin II.

https://science.sciencemag.org/content/sci/196/4296/1313.full.pdf

Rat Insulin Genes: Construction of Plasmids Containing the Coding Sequences

The evolution of genes: the chicken preproinsulin gene

Determination of the amino acid sequence of the monkey, sheep, and dog proinsulin C-peptides by a semi-micro Edman degradation procedure.

Studies on the Conversion of Proinsulin to Insulin III. STUDIES IN VITRO WITH A CRUDE SECRETION GRANULE FRACTION ISOLATED FROM RAT ISLETS OF LANGERHANS

SUMMARY 1. The metabolism of unlabelled monocomponent human insulin and porcine proinsulin was studied in ten normal subjects (five males and five females) by using a priming dose-constant-infusion technique. In each subject, the metabolic clearance rate (MCR) was measured at four separate steady-state hormone concentrations averaging 16-21 6 punitslml (insulin) and 4-2-42.8 ng/ml (proinsulin). 2. For insulin the MCR fell progressively from 34 ml kg-' min-' at a mean fasting insulin concentration of 3.8 punitslml to 11.4 ml kg-' min-' at the highest concentration achieved (280 punits/ml); for proinsulin MCR averaged 3.7 ml kg - ' min-' at a mean plasma concentration of 4.2 ng/ml and fell to 2.71 ml kg-' min-' at 10.7 ng/ml, remaining constant thereafter at concentrations up to 71 ng/ml. 3. The half-disappearance time (T+) from the plasma, after the end of the infusion, averaged 4.3 min for insulin and 25.6 min for proinsulin. 4. The apparent distribution space (DS) was similar for both hormones (83 ml/kg of insulin and 98.9 ml/kg of proinsulin). 5. There was a direct correlation between T+ and DS for both hormones. 6. Although the higher MCR of insulin was reflected in its shorter T+, there was, for each hormone, no relationship between MCR and T+. 7. The biological potency of porcine proinsulin, as judged by its effect on plasma glucose, was approximately 5% of that of insulin. 8. The responses of serum growth hormone and cortisol were shown to be directly related to the degree of hypoglycaemia induced.

A comparative study on the metabolism of human insulin and porcine proinsulin in man.

The determination of the amino acid sequence of the C-peptide of human proinsulin is presented. Two constituent fragments of C-peptide, Chy 1 + 2 and Chy 3 (residues 1–24 and 25–31, respectively) were liberated by mild chymotryptic digestion and isolated by gel filtration and ion exchange chromatography. From Chy 1 + 2 was obtained seven smaller peptides by further digestion with chymotrypsin. The sequence analysis of these fragments allowed an overall structure to be assigned. Papain digestion of the intact C-peptide provided 12 peptides, the compositions of which provided unequivocal confirmation for the proposed sequence.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1971.tb01378.x

The Amino Acid Sequence of the C‐Peptide of Human Proinsulin

The amino acid sequences of two rat C-peptides corresponding to two rat proinsulins have been elucidated. Both C-peptides have 31 amino acids. There are differences in two positions, namely, in position 8 where rat-I has a proline and rat-II an alanine residue, and in position 17 where rat-I has a glutamic acid, rat-II a glycine residue. The additional acidic residue in rat-I C-peptide is counteracted by the additional basic residue in the insulin moiety of rat-I proinsulin (lysine B 29), which provides the two proinsulins with the same net charge at neutral pH.



The amino acid sequences are: 








The rat C-peptides contain threonine and arginine, neither of which is present in the C-peptides of man, pig and ox.



A comparison of the 5 sequences shows only 10 identical positions out of 31.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1972.tb01680.x

Rat-proinsulin C-peptides. Amino-acid sequences.

The two rat proinsulins have been separated and the amino acid compositions determined.



Using a method previously described for preparing C-peptides from ox and pork pancreases, three peptides were isolated from rat pancreases and the amino acid compositions of these peptides determined.



Data are presented which strongly indicate that two of these peptides constitute the C-peptide part of the connecting peptide of the two rat proinsulins.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1972.tb01679.x

Rat Proinsulins and C-Peptides

The amino acid sequence of the proinsulin C-peptide isolated from bovine pancreas has been determined and the experimental data is presented. Digestion of C-peptide with chymotrypsin provided three fragments, the compositions of which accounted for the whole structure. Digestion of the three peptides with papain gave rise to a variety of small peptides, which were isolated. The sequences of the chymotrypsin and papain peptides allowed the primary structure of bovine C-peptide to be assigned. The similarity of the sequence obtained for C-peptide isolated from bovine pancreas with that written for C-peptide from bovine proinsulin provides strong evidence for their identity. The sequence presented contains two differences from that cited previously.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1971.tb01377.x

Bovine Proinsulin: Amino Acid Sequence of the C‐Peptide Isolated from Pancreas

Duck insulin was isolated and crystallized, and its amino acid sequence was elucidated. A comparison with chicken insulin, the only avian insulin so far sequenced, shows three differences. In the A-chain, duck insulin has glutamic acid at position 8 and proline at position 10, where chicken insulin exhibits histidine and threonine, respectively. In the B-chain, the only difference in sequences is located at position 30, where duck insulin has a threonine residue while chicken insulin has an alanine residue.

Finn Sundby

Papers

The Amino Acid Sequence of the C‐Peptide of Human Proinsulin

Rat-proinsulin C-peptides. Amino-acid sequences.

Rat Proinsulins and C-Peptides

Bovine Proinsulin: Amino Acid Sequence of the C‐Peptide Isolated from Pancreas

Duck insulin: isolation, crystallization and amino acid sequence