SEMISYNTHETIC INSULIN ANALOGS MODIFIED IN POSITIONS B24, B25 AND B29

New semisynthetic analogues of human insulin, modified in the C-termin al region of the B-chain, were prepared to refine our understanding of the importance of particular amino acid residues in the expression of hormone biological properties. The following insulin analogues were s ynthesized by trypsin-catalyzed peptide-bond formation between the C-t erminal arginine(B22) of des-octapeptide(B23-B30)-insulin and syntheti c octapeptides with the epsilon-amino group of lysine(B29) protected b y a phenylacetyl group: [L,Lys(pac)B29]insulin, [D-phe(B24,B25), L-Lys (Pac)(B29)]insulin and [D-Phe(p-Et)(B24),L-Lys(Pac)(B29)]insulin. Enzy matic deprotection using immobilized penicillin amidohydrolase yielded : human insulin, [D-phe(B24,B25)]insulin and [Dphe(p-Et)(B24)]-insulin . Biological in vitro potencies (specific binding to cultured human ly mphocytes IM-9 and lipogenic potency in isolated rat adipocytes) of th e semisynthetic analogues were estimated, ranging from 0.2 to 100% rel ative to porcine insulin.