Conformational Properties of Gluten Exorphins GE-A and its Role when Encrypted in Precursor Protein.

Many kinds of bioactive peptides have been found in the enzymatic digest of food proteins; some of these are of animal origin, such as ?-casomorphin and hemorphins, some are of plant origin such as gluten exorphins. Interestingly, opioid peptides derived from animal proteins are mostly ?-receptors selective, while those of plant origin are mostly ?-receptors selective. Activities profiles obtained with a cyclic enkephalin analogue and its linear correlate revealed that ?- and ?-receptors differs on their conformational requirements. Gluten exorphins are opioid peptides isolated from enzymatic digest of wheat gluten and can be classified into three groups according to their structure, namely, gluten exorphin A, GE-A, gluten exorphin B, GE-B, gluten exorphin C, GE-C. There are two members of GE-A which are GE-A5 (GYYPT) and GE-A4 (GYYP). The structure of GE-A is unique in that, unlike most opioid peptides which have Tyr in their N-terminus, GE-A has a Gly in N-terminus (essential for opioid activity). In our work on synthetic opioid peptides we studied the conformational behaviour in solution of conventionally protected gluten exorphins sequences.[1] These product have been synthesized, purified, and then analysed by NMR spectroscopy.[2] We described here the chloroform solution NMR analysis of Boc-GYYP-OMe (1) and Boc-GYYPT-OMe (2). The initial NMR analysis of the synthetic tetrapeptide 1 clearly indicate the coexistence of two different conformation in equilibrium. The results on the conformational characterization of both structures will describe in this work. Furthermore, we analyse the influence of conformational characteristics of tetrapeptide 1 on the structure of wheat glutenin. The understanding of the role and organization structural of the natural protein permitted the design of delivery systems containing the bioactive sequence. References 1. G. Fanciulli, A. Dettori, E. Fenude, E. Alberico, Pharmacological Research 2003, 47, 53. 2. E. Fenude, S.Dedola, M. Fais VII Congress "Complex Systems: structure, properties, reactivity and dynamics" (2005), Alghero, Italy.