Pressure/temperature combined treatments of precursors yield hormone-like peptides with pyroglutamate at the N terminus.
Peptides containing the cyclic product of glutamine at the N terminus are usually biologically active. If the cyclization of glutamine was associated with a volume reduction, pressure should displace the equilibrium in the direction of the lower volume. Here, results in model solutions and in whey are discussed, showing that the theorized cyclization of glutamine in Gln-His-ProNH(2) or Gln-Leu-ProNH(2) is significantly accelerated during the application of heat and even more strongly when elevated temperature and pressure combinations are used. The reaction rate depended on the intensity of the pressure treatment, the pH, and the nature of the amino acids adjacent to glutamine. The products of the reaction were identified as thyrotropin-releasing hormone (TRH) and [Leu(2)]TRH. The reported reactions could affect the naturally balanced concentration of short-chain peptides in foods and therefore induce unpredictable biological effects.
Fernández García
Avelina
A
Institute of Chemistry and Biology, Federal Research Centre for Nutrition, Haid-und-Neustrasse 9, D-76131 Karlsruhe, Germany. veli.fernandez@bfe.uni-karlsruhe.de
Butz
Peter
P
Trierweiler
Bernhard
B
Zöller
Heike
H
Stärke
Joachim
J
Pfaff
Eberhard
E
Tauscher
Bernhard
B
D003500:Cyclization; D005973:Glutamine / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D036361:Peptide Hormones / Q000737:chemistry*; D011312:Pressure; D011498:Protein Precursors / Q000737:chemistry*; D011761:Pyrrolidonecarboxylic Acid / Q000032:analysis*; D012996:Solutions; D013973:Thyrotropin-Releasing Hormone / Q000737:chemistry
D036361:Peptide Hormones; D011498:Protein Precursors; D012996:Solutions; D005973:Glutamine; D013973:Thyrotropin-Releasing Hormone; D011761:Pyrrolidonecarboxylic Acid