Semisynthesis and biological properties of the [B24-leucine]-, [B25-leucine[- and [B24-leucine, B25-leucine]-analogues of human insulin.

Trypsin-catalyzed coupling of porcine desoctapeptide-insulin with synthetic octapeptides produced the [LeuB24]- (I), [LeuB25]- (II) and [LeuB24, LeuB25]- (III)analogues of human insulin. I, II and III displayed respectively 20--30%, 1--2% and 0.5% of the receptor binding activity of the normal hormone. Biological activities of these analogues seemed to be proportional to their binding potencies when assayed in vitro, while in an in vivo assay analogue I was fully active and II exhibited 10--20% of normal activity. III was less active than II in all assays tested.