CHEMICAL SYNTHESIS OF [DES(TETRAPEPTIDE B27–30), TYR(NH2)26‐B] AND [DES(PENTAPEPTIDE B26–30), PHE(NH2)25‐B] BOVINE INSULINS*

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Abstract
Two analogs of bovine insulin, [des(tetrapeptide B27–30), Tyr(NH2)26‐B] and [des(pentapeptide B26–30), Phe(NH2)25‐B] insulin, which differ from the parent molecule in that the C‐terminal tetrapeptide and pentapeptide sequences, respectively, from the B chain have been eliminated and the newly exposed residues are amidated, have been synthesized. The [des(tetrapeptide B27–30), Tyr(NH2)26‐B] insulin shows potencies of 16.8 IU/mg by the mouse convulsion assay method and 10.8 IU/mg by the radioimmunoassay method. The [des(pentapeptide B26–30), Phe(NH2)25‐B] insulin possesses a potency of 10.5 IU/mg when assayed by the mouse convulsion method and 14 IU/mg by the radioimmunoassay technique. The potencies of these analogs are higher than the potencies of the respective non‐amidated derivatives (Katsoyannis et al., 1973, 1974). It is speculated that the gradual decline of biological activity observed as amino acid residues are eliminated from the C‐terminal region of the B chain of insulin is due to the proximity of a hydrophilic carboxyl group to the hydrophobic core of the protein molecule.

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