Structure-activity studies of orexin a and orexin B at the human orexin 1 and orexin 2 receptors led to orexin 2 receptor selective and orexin 1 receptor preferring ligands

J Med Chem. 2004 Feb 26;47(5):1153-60. doi: 10.1021/jm030982t.


The neuropeptides orexin A and B (also known as hypocretins) play an important role in many physiological and behavioral activities. Orexins are ligands of two closely related G-protein-coupled receptors, that are the named orexin 1 and orexin 2 receptors. To clearly identify the minimal ligand sequences required for receptor activation, we synthesized and analyzed different centrally, C- and N-terminally truncated analogues of orexins A and B. Furthermore, we used the shortest active analogue to screen for important amino acid residues by l-alanine and l-proline replacement scans. For orexin A, only full-length peptides were able to show the same activity as orexin A, but interestingly, reduced orexin A and natural orexin A, which contains the two disulfide bonds, had the same activity. The shortest highly active orexin B analogue was orexin B 6-28. In addition, we identified orexin A 2-33 as the first analogue with orexin 1 receptor preference and orexin B 10-28, [A27]orexin B 6-28, and [P11]orexin B 6-28 as being highly potent orexin 2 receptor selective (>1000-fold) peptides.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism
  • Carrier Proteins / chemistry
  • Carrier Proteins / pharmacology*
  • Cell Line
  • Humans
  • Intracellular Signaling Peptides and Proteins*
  • Neuropeptides / chemistry
  • Neuropeptides / pharmacology*
  • Oligopeptides / chemical synthesis*
  • Oligopeptides / chemistry
  • Oligopeptides / pharmacology
  • Orexin Receptors
  • Orexins
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / chemistry
  • Peptide Fragments / pharmacology
  • Receptors, G-Protein-Coupled
  • Receptors, Neuropeptide / drug effects*
  • Receptors, Neuropeptide / metabolism
  • Structure-Activity Relationship


  • Carrier Proteins
  • HCRT protein, human
  • Intracellular Signaling Peptides and Proteins
  • Neuropeptides
  • Oligopeptides
  • Orexin Receptors
  • Orexins
  • Peptide Fragments
  • Receptors, G-Protein-Coupled
  • Receptors, Neuropeptide
  • Calcium