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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Hemopressin (Hp) is an alpha hemoglobin fragment with the sequence PVNFKFLSH, originally identified in extracts of rat brain using an enzyme capture technique. It binds cannabinoid receptors, acting as an inverse agonist at CB1 receptors. Longer forms of hemopressin containing 2-3 additional amino acids on the N-terminus have been identified in extracts of mouse brain. These longer hemopressin peptides, named RVD-Hpα and VD-Hpα, bind to CB1 receptors and are agonists. In addition to the Hp peptides from alpha hemoglobin, a related peptide from beta hemoglobin has been found in mouse brain extracts; this peptide, named VD-Hpβ, is also an agonist at CB1 cannabinoid receptors.
The original Hp peptide reduces sensitivity to painful stimuli in an experimental model of hyperalgesia. Hp also reduces food intake in mice. However, it remains to be shown if Hp is an endogenous brain peptide. The original purification used boiling acid to extract the peptide from rat brain, and hot acid can specifically cleave D-P bonds. The N-terminally-extended forms RVD-Hpα and VD-Hpα may represent the true endogenous forms.
Role in diet 
Scientists at the University of Manchester have discovered that hemopressin could be used as an appetite suppressant without having the side effects of many other drugs that are used for this purpose. In laboratory tests hemopressin was administrated to mice and rats, which significantly reduced food intake. Hemopressin works by affecting the reward centres of the brain which make us feel happy when we eat too much. A further research should be carried out in order to confirm these effects and the safety on people.
See also 
- Rioli V, Gozzo FC, Heimann AS, et al. (March 2003). "Novel natural peptide substrates for endopeptidase 24.15, neurolysin, and angiotensin-converting enzyme". J. Biol. Chem. 278 (10): 8547–55. doi:10.1074/jbc.M212030200. PMID 12500972.
- Heimann AS, Gomes I, Dale CS, et al. (December 2007). "Hemopressin is an inverse agonist of CB1 cannabinoid receptors". Proc. Natl. Acad. Sci. U.S.A. 104 (51): 20588–93. Bibcode:2007PNAS..10420588H. doi:10.1073/pnas.0706980105. PMC 2154475. PMID 18077343.
- Gomes I, Grushko JS, Golebiewska U, et al. (September 2009). "Novel endogenous peptide agonists of cannabinoid receptors". FASEB J. 23 (9): 3020–9. doi:10.1096/fj.09-132142. PMC 2735371. PMID 19380512.
- Dale CS, Pagano Rde L, Rioli V, et al. (March 2005). "Antinociceptive action of hemopressin in experimental hyperalgesia". Peptides 26 (3): 431–6. doi:10.1016/j.peptides.2004.10.026. PMID 15652650.
- Dodd GT, Mancini G, Lutz B, et al. (May 2010). "The peptide hemopressin acts through CB1 cannabinoid receptors to reduce food intake in rats and mice". J Neurosci. 30 (21): 7369–76. doi:10.1523/JNEUROSCI.5455-09.2010. PMID 20505104.
- Gelman JS, Sironi J, Castro LM, et al. (May 2010). "Hemopressins and other hemoglobin-derived peptides in mouse brain: comparison between brain, blood, and heart peptidome and regulation in Cpefat/fat mice". J Neurochem. 113 (4): 871–80. doi:10.1111/j.1471-4159.2010.06653.x. PMID 20202081.