title: Occurrence of the free and Peptide forms of pyroglutamic acid in plasma from the portal blood of rats that had ingested a wheat gluten hydrolysate containing pyroglutamyl peptides.
abstract: In order to determine pyroglutamic acid levels in plasma, we developed a method based on precolumn derivatization of the carboxyl group of pyroglutamic acid with 2-nitrophenylhydrazine. Eight-week-old male SD strain rats were administered 200 mg of an acidic peptide fraction obtained from a commercial wheat gluten hydrolysate containing 0.63 mmol/g pyroglutamyl peptide. After administration, significant amounts of free pyroglutamic acid were observed in the ethanol-soluble fraction of the plasma from the portal vein. In addition, pyroglutamate aminopeptidase digestion of the ethanol-soluble fraction liberated significant amounts of pyroglutamic acid, which indicated the presence of the pyroglutamyl peptide. The presence of the pyroglutamyl peptide in the plasma was further confirmed by size exclusion chromatography. The levels of free and peptide forms of pyroglutamic acid increased significantly and reached a maximum (approximately 40 nmol/mL) at 15 and 30 min after administration, respectively.
authors.affiliation: Department of Food Sciences & Nutritional Health, Kyoto Prefectural University, 1-5 Shimogamo, Kyoto 606-8522, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Higaki-Sato
authors.forename: Kenji
authors.initials: K
authors.lastname: Sato
authors.forename: Naomi
authors.initials: N
authors.lastname: Inoue
authors.forename: Yuko
authors.initials: Y
authors.lastname: Nawa
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kido
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Nakabou
authors.forename: Kaori
authors.initials: K
authors.lastname: Hashimoto
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Kozo
authors.initials: K
authors.lastname: Ohtsuki
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D005983:Glutens / Q000008:administration & dosage* / Q000737:chemistry*; D006868:Hydrolysis; D008297:Male; D010455:Peptides / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism; D011169:Portal Vein; D011751:Pyroglutamyl-Peptidase I / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000008:administration & dosage* / Q000097:blood* / Q000737:chemistry; D051381:Rats; D014908:Triticum / Q000737:chemistry*
chemical_list: D010455:Peptides; D005983:Glutens; D011751:Pyroglutamyl-Peptidase I; D011761:Pyrrolidonecarboxylic Acid