Monday, August 17, 2009

Gluten Exorphins

Definition
Gluten exorphins are peptides isolated from pepsin hydrolysates of Wheat gluten. They have morphine-like opioid activity and can act like the body's own narcotics, the endorphins1.

Related peptides
Four gluten exorphins were isolated from the enzymatic digest of wheat gluten and were named gluten exorphins A5, A4, B5 and B42.

Discovery
Zioudrou et al. (1979) identified some opioid peptides in the digests of wheat prolamines with endorphin like activity and termed them “exorphins”. Fukudome and Yoshikawa (1992) have since characterized 15 separate amino acid sequences of gluten-exorphin A-5 in a single molecule of wheat1.2.

Structural characteristics
Gluten exorphins A5 (Gly-Tyr-Tyr-Pro-Thr), A4 (Gly-Tyr-Tyr-Pro), B5 (Tyr-Gly-Gly-Trp-Leu) and B4 (Tyr-Gly-Gly-Trp) were isolated from the enzymatic digests of wheat gluten. The structure-activity relationships of gluten exorphins A are unique. The presence of Gly at their N-termini increases their potency. Gluten exorphin B5, which corresponds to [Trp4,Leu5]- enkephalin, shows the most potent activity among these peptides3.

Mechanism of action
In order for exorphins to function as opioid peptides in the central nervous system in vivo they must (a) be produced in the gastrointestinal tract, (b) survive degradation by intestinal proteases, (c) be absorbed, without degradation, into the bloodstream, (d) cross the blood-brain barrier and thereby reach central opiate receptors, and (e) interact as opiates with these receptors2.

Function
Gluten exorphins, which are exogenous opioids, bind to the same cellular receptors that endogenous opioids bind to, thus impacting on the immune system, nerve function, myelination processes, vascular walls, neuromuscular function, and a variety of CNS functions. Such opioids can have an anaesthetizing, analgesic, and addictive effect1.

References
1.Book: The book of Gluten by Stephen J Gislason, Gislason, Stephen J.
2.Fukudome S, Yoshikawa M (1993). Opioid peptides derived from wheat gluten: their isolation and characterization. FEBS Letters, 316:17-19.
3.Zioudrou C, Streaty RA, Klee WA (1979). Opioid peptides derived from food proteins. The exorphins. J. Biol. Chem. 254:2446-2449.

1 comment:

hopeful geranium said...

This may seem far-fetched but I believe needs to be at least checked out; there is a high degree of association between symp toms and syndromes of celiac disease and hepatitis C. There are iummunological reasons why this should be so in about 3% of cases, but the actual correspondence seems greater.
Could it be that HCV core protein includes peptide sequences similar to gliadomorphins and casomorphins? In this case chronic Hep C might trigger autoimmune reactions to gluten peptides in individuals without genetic predisposition to celiac, or the same disease could be caused by the viral peptides.