PROTEASE-CATALYZED CONDENSATION-OLIGOMERIZATION OF HYDROPHOBIC PEPTIDES AS A MEANS OF FLAVOR MODIFICATION

Hydrophobic peptides such as Val-Leu, Gly-Leu and Ser-Leu can undergo a protease-catalysed condensation reaction in water or aqueous ethanol . The enzyme catalyses an equilibrium between peptide bond formation a nd breakage, and the reaction appears to be driven towards condensatio n by precipitation of the products. Electrospray mass spectroscopy (ES MS) of the products showed them to be oligomers of the starting peptid e from the dimer up to as far as the heptamer, the tetramer generally being the major product. If the starting dipeptide is bitter, the olig omers are much less so. Monitoring of the reaction was undertaken usin g C-13-NMR analysis of 1 - C-13-labelled marker peptides. This allowed precise determination of the extent of reaction under various conditi ons. This nuclear magnetic resonance (NMR) technique may be applicable to the study of peptide bond rearrangement in a variety of complex mi xtures. (C) 1998 Published by Elsevier Science B.V. All rights reserve d.