[12-asparagine-B] human insulin. An analogue with modification in the hydrophobic core of insulin

The human [12-Asparagine-B] insulin [Asn12-B] insulin) which differs from the parent molecule in that the valine residue at position B12 is substituted by an asparagine residue, has been synthesized by the procedures developed in this laboratory. In stimulating glucose oxidation and lipogenesis the analogue exhibited potencies of 0.19% and 0.14%, respectively, as compared to insulin. In insulin receptor binding [Asn12-B] insulin was found to possess a potency of ca. 0.29% compared to the natural hormone. At high concentrations this analogue is shown to have the same maximal activity in the in vitro assays as the natural hormone. This indicates that despite the low affinity for of the analogue for the insulin receptor, the analogue-receptor complex is fully capable of initiating the series of chemical events that leads to the biological response. It is concluded that the B12 valine contributes greatly in the maintenance of a structure possessing the proper receptor-binding characteristics, but does not have any role in modulating the activity of the hormone-receptor complex. The potency of this analogue by radioimmunoassay is at least 100-fold higher than the in vitro biological assays, indicating that the immunological determinants of insulin can be essentially unrelated to the biological activity of the molecule.