Definition
Beta-Casomorphins are peptides resulting from the digestion of beta-Casein and vary from 4-11 amino acids in length1. They exhibit opioid or morphine-like functions1.
Discovery
ß-Casomorphins were first purified from casein digest of guinea pig ileum based on their ability to show opioid activity2.
Classification
ß-Casomorphins are opioid peptides1. Several naturally occurring ß-Casomorphins (BCM) have been identified: Bovine BCM-4, Bovine BCM-5, Bovine BCM-6, Bovine BCM-7, Bovine BCM-8, Bovine BCM-11, Human BCM-7, Human BCM-81. Several analogues which are structurally modified variants of naturally occurring BCMs have been synthesized1.
Structural Characteristics
BCMs are 4-11 amino acids in length. The sequences of naturally occurring BCMs are given below1:
Bovine BCM-4 Tyr-Pro-Phe-Pro,
Bovine BCM-5 Tyr-Pro-Phe-Pro-Gly
Bovine BCM-6 Tyr-Pro-Phe-Pro-Gly-Pro
Bovine BCM-7 Tyr-Pro-Phe-Pro-Gly-Pro-Ile
Bovine BCM-8 Tyr-Pro-Phe-Pro-Gly-Pro-Ile-Pro
Bovine BCM-11 Tyr-Pro-Phe-Pro-Gly-Pro-Ile-Pro-Asn-Ser-Leu
Human BCM-7 Tyr-Pro-Phe-Val-Glu-Pro-Ile
Human BCM-8 Tyr-Pro-Phe-Val-Glu-Pro-Ile-Pro
Some sequences of BCM analogues are shown below3:
H-Tyr-Pro-Phe-Pro-Gly-EtDA-Gly-II
H-Tyr-Pro-Phe-Pro-Gly-EtDA-Gly-Gly-II
H-Tyr-Pro-Phe-Pro-Gly-EtDA-Gly-Gly-CO-CH3
H-Tyr-Pro-Phe-Pro-Gly-EtDA-Gly-Gly-CO-CH2-CH2-COOH
Mode of action
Not much has been studies on the exact mechanism of BCM function. It is known that they exert their opioid functions by binding to opioid receptors on cell membranes4. Recent studies have shown that BCM-7 is a high affinity ligand for angiotensin receptor in the brain4.
Functions
BCMs produce effects in the gastrointestinal tract. For instance they influence post prandial metabolism by stimulating the secretion of insulin and somatostatin and modulate transfer of amino acids in the intestine5. The affect hypoxia as it has been shown that BCM7 when administered to pregnant rats induces their recovery from hypoxic condition4. BCM-5 and analogs are involved in producing rotational behavior in rats6. BCM-8 is involved in interplay between mother and child during lactation7. Finally, BCMs have been implicated in several diseases including SIDS and childhood autism1.
References
1. Kamiñski S, Cieoeliñska A, Kostyra E (2007). Polymorphism of bovine beta-casein and its potential effect on human health. J Appl Genet, 48(3), 189–198.
2. Ramabadran K, Bansinath M (1989). Pharmacology of beta-casomorphins, opioid peptides derived from milk protein. Asia Pac J Pharmacol, 4, 45–58.
3. Sobirov MM, Khalikov ShKh, Saidov SS, Kodirov MZ, Zaitsev SV, Chichenkov ON, Varfolomeev SD (1994). Synthesis and biological activity of new analogs of beta-casomorphine-5. Bioorg Khim., 20(7), 740-50.
4. Book: Handbook of Biologically Active Peptides by Abba J. Kastin.
5. Zoghbi S, Trompette A, Claustre J, Homsi ME, Garzo´n J, Jourdan G, Scoazec JY and Plaisancie P (2006). Casomorphin-7 regulates the secretion and expression of gastrointestinal mucins through a opioid pathway. Am J Physiol Gastrointest Liver Physiol 290, G1105–G1113.
6. Marschitz HM, Terenius L, Grehn L, Ungerstedt U (1989). Rotational behaviour produced by intranigral injections of bovine and human beta-casomorphins in rats. Psychopharmacology (Berl), 99(3), 357-61.
7. Ivano DN, Richard JF, Hannu JTK, Yves LR, Chris TL, Inga T, Daniel T, Renger W, (2009). Review of the potential health impact of ß-casomorphins and related peptides. EFSA Scientific Report, 231, 1-107.