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HMDB Protein ID HMDBP02340
Secondary Accession Numbers
  • 7828
Name Orexin
  1. Hcrt
  2. Hcrt1
  3. Hcrt2
  4. Hypocretin
  5. Hypocretin-1
  6. Hypocretin-2
  7. Orexin-A
  8. Orexin-B
Gene Name HCRT
Protein Type Enzyme
Biological Properties
General Function Involved in neuropeptide signaling pathway
Specific Function Neuropeptides that play a significant role in the regulation of food intake and sleep-wakefulness, possibly by coordinating the complex behavioral and physiologic responses of these complementary homeostatic functions. A broader role in the homeostatic regulation of energy metabolism, autonomic function, hormonal balance and the regulation of body fluids, is also suggested. Orexin-A binds to both OX1R and OX2R with a high affinity, whereas orexin-B binds only to OX2R with a similar high affinity
Pathways Not Available
Reactions Not Available
GO Classification
response to stimulus
feeding behavior
neuropeptide signaling pathway
signaling pathway
cell surface receptor linked signaling pathway
g-protein coupled receptor protein signaling pathway
Cellular Location
  1. Cytoplasmic vesicle
  2. Cell junction
  3. synapse
  4. Rough endoplasmic reticulum
Gene Properties
Chromosome Location Chromosome:1
Locus 17q21
Gene Sequence
>396 bp
Protein Properties
Number of Residues 131
Molecular Weight 13362.5
Theoretical pI 11.35
Pfam Domain Function
  • 1-33
Transmembrane Regions
  • None
Protein Sequence
GenBank ID Protein Not Available
UniProtKB/Swiss-Prot ID O43612
UniProtKB/Swiss-Prot Entry Name OREX_HUMAN
GenBank Gene ID AF041240
GeneCard ID HCRT
GenAtlas ID HCRT
General References
  1. Sakurai T, Amemiya A, Ishii M, Matsuzaki I, Chemelli RM, Tanaka H, Williams SC, Richardson JA, Kozlowski GP, Wilson S, Arch JR, Buckingham RE, Haynes AC, Carr SA, Annan RS, McNulty DE, Liu WS, Terrett JA, Elshourbagy NA, Bergsma DJ, Yanagisawa M: Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior. Cell. 1998 Feb 20;92(4):573-85. [PubMed:9491897 ]
  2. Sakurai T, Moriguchi T, Furuya K, Kajiwara N, Nakamura T, Yanagisawa M, Goto K: Structure and function of human prepro-orexin gene. J Biol Chem. 1999 Jun 18;274(25):17771-6. [PubMed:10364220 ]
  3. Lee JH, Bang E, Chae KJ, Kim JY, Lee DW, Lee W: Solution structure of a new hypothalamic neuropeptide, human hypocretin-2/orexin-B. Eur J Biochem. 1999 Dec;266(3):831-9. [PubMed:10583376 ]
  4. Hungs M, Mignot E: Hypocretin/orexin, sleep and narcolepsy. Bioessays. 2001 May;23(5):397-408. [PubMed:11340621 ]
  5. Willie JT, Chemelli RM, Sinton CM, Yanagisawa M: To eat or to sleep? Orexin in the regulation of feeding and wakefulness. Annu Rev Neurosci. 2001;24:429-58. [PubMed:11283317 ]
  6. Kim HY, Hong E, Kim JI, Lee W: Solution structure of human orexin-A: regulator of appetite and wakefulness. J Biochem Mol Biol. 2004 Sep 30;37(5):565-73. [PubMed:15479620 ]
  7. Siebold C, Hansen BE, Wyer JR, Harlos K, Esnouf RE, Svejgaard A, Bell JI, Strominger JL, Jones EY, Fugger L: Crystal structure of HLA-DQ0602 that protects against type 1 diabetes and confers strong susceptibility to narcolepsy. Proc Natl Acad Sci U S A. 2004 Feb 17;101(7):1999-2004. Epub 2004 Feb 9. [PubMed:14769912 ]
  8. Takai T, Takaya T, Nakano M, Akutsu H, Nakagawa A, Aimoto S, Nagai K, Ikegami T: Orexin-A is composed of a highly conserved C-terminal and a specific, hydrophilic N-terminal region, revealing the structural basis of specific recognition by the orexin-1 receptor. J Pept Sci. 2006 Jul;12(7):443-54. [PubMed:16429482 ]
  9. Peyron C, Faraco J, Rogers W, Ripley B, Overeem S, Charnay Y, Nevsimalova S, Aldrich M, Reynolds D, Albin R, Li R, Hungs M, Pedrazzoli M, Padigaru M, Kucherlapati M, Fan J, Maki R, Lammers GJ, Bouras C, Kucherlapati R, Nishino S, Mignot E: A mutation in a case of early onset narcolepsy and a generalized absence of hypocretin peptides in human narcoleptic brains. Nat Med. 2000 Sep;6(9):991-7. [PubMed:10973318 ]