Synthetic linear and cyclic glucagon antagonists

RAMALINGA DHARANIPRAGADA, DEV TRIVEDI, ANNE BANNISTER, MARA SIEYEL, DIRK TOURWE, NEVENA MOLLOVA, KARL SCHRAM, VICTOR J. HRUBY

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

The synthesis and biological activities of seven new glucagon analogues are reported. The design of com‐ pounds 2‐5 is based on potent antagonists recently reported from this laboratory, where we have focused on modifications in the N‐terminal region. In this report we have concentrated specifically on modifications to histidine‐1. In addition we have prepared two cyclic compounds 7 and 8, related to a linear in vivo antagonist [Glu9]glucagon, reported by Medeld (Unson et al. (1987) Proc. Natl. Acad. Sci. USA84, 4083‐4087). The N‐terminal modifications involved substitution of His1 by the unnatural conformationally constrained residue (S)‐5,6,7,8‐tetrahydro‐5‐oxoimidazo(1,5‐c)pyrimidine‐7‐carboxylic acid (Toc), desaminohistidine (dHis) and 3‐(4‐nitrobenzyl)histidine. The structures of the new compounds are as follows. [Toc1,d‐Phe4,Tyr5,Arg12,Lys17,18,Glu21]glucagon (2); [Toc1,dPhe4,Tyr5,Arg12,Lys17,18,Glu21]glucagon amide (3); [3‐(4‐nitrobenzyl)His1,dPhe4,Tyr5,Arg12,Lys17,18,Glu21]glucagon (4); [dHis1,d‐Phe4,Tyr5,Arg12,Lys17,18,Glu21]glucagon (5); [dHis1,Glu9]glucagon (6); (desHis1)glucagon amide (7); (desHis1)‐glucagon amide (8). The binding potencies of the linear analogues, as expressed a percentage of glucagon binding, are 2.6 (2), 0.13 (3), 0.8 (4), 0.8 (5), 2.2 (6). Both cyclic analogues 7 and 8 show biphasic binding curves. The IC50 values for 7 at the high and low finity sites are 1.5 and 167 nm, respectively (IC50 of glucagon = 1.3 nm). The IC50 values for 50 at the high and low affinity sites are 4.7 and 3451 nm, respectively. The cyclic analogues are characterized by fast atom bombardment mass spectrometry of endoproteinase ASP‐N digests. The specificity of the enzyme used in these studies enables differentiation of isomers of the cyclic glucagon analogues which differ only in the position of cyclic amide bond. Analogues 2,3 and 5–8 are glucagon receptor antagonists with respect to the glucagon receptor coupled to the adenylate cyclase (AC) system. Analogue 4 is a partial agonist (5.7% compared to glucagon) of AC. Introduction of unusual amino acids which do not contain a primary α‐amino group such as Toc at the N‐terminus is expected to increase in vivo metabolic stability by protecting against degradation by aminopeptidases.

Original languageEnglish (US)
Pages (from-to)68-77
Number of pages10
JournalInternational journal of peptide and protein research
Volume42
Issue number1
DOIs
StatePublished - Jul 1993

Keywords

  • FAB mapping
  • conformational constraints
  • enzymatic digestion
  • glucagon analogues
  • glucagon antagonists
  • structure‐activity relationships
  • unusual amino acids

ASJC Scopus subject areas

  • Biochemistry

Fingerprint Dive into the research topics of 'Synthetic linear and cyclic glucagon antagonists'. Together they form a unique fingerprint.

  • Cite this

    DHARANIPRAGADA, RAMALINGA., TRIVEDI, DEV., BANNISTER, ANNE., SIEYEL, MARA., TOURWE, DIRK., MOLLOVA, NEVENA., SCHRAM, KARL., & HRUBY, VICTOR. J. (1993). Synthetic linear and cyclic glucagon antagonists. International journal of peptide and protein research, 42(1), 68-77. https://doi.org/10.1111/j.1399-3011.1993.tb00352.x