Studies on N-terminal glycation of peptides in hypoallergenic infant formulas: quantification of alpha-N-(2-furoylmethyl) amino acids.
To obtain information about the extent of the early Maillard reaction between the N-termini of peptides and lactose, alpha-N-(2-furoylmethyl) amino acids (FMAAs) were quantified together with epsilon-N-(2-furoylmethyl)lysine (furosine) in acid hydrolyzates of hypoallergenic infant formulas, conventional infant formulas, and human milk samples using RP-HPLC with UV-detection. FMAAs are formed during acid hydrolysis of peptide-bound N-terminal Amadori products (APs), and furosine is formed from the Amadori products of peptide-bound lysine. Unambiguous identification was achieved by means of LC/MS and UV-spectroscopy using independently prepared reference material. The extent of acid-induced conversion of APs to FMAAs was studied by RP-HPLC with chemiluminescent nitrogen detection (CLND). Depending on the corresponding alpha-N-lactulosyl amino acid, between 6.0% and 18.1% of FMAAs were formed during hydrolysis for 23 h at 110 degrees C in 8 N HCl. From epsilon-N-lactulosyllysine, 50% furosine is formed under these conditions. Whereas furosine was detectable in all assayed samples, five different FMAAs, alpha-FM-Lys, alpha-FM-Ala, alpha-FM-Val, alpha-FM-Ile, and alpha-FM-Leu, were exclusively detected in acid hydrolyzates of hypoallergenic infant formulas in amounts ranging from 35 to 396 mumol/100 g protein. Taking the conversion factors into account, modification of N-terminal amino acids in peptides by reducing carbohydrates was between 0.3% and 8.4%. This has to be considered within the discussion concerning the nutritional quality of peptide-containing foods.
Penndorf
Ilka
I
Institute of Food Chemistry, Technische Universität Dresden, Bergstrasse 66, D-01062 Dresden, Germany.
Biedermann
Daniela
D
Maurer
Sarah V
SV
Henle
Thomas
T
D000596:Amino Acids / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D005512:Food Hypersensitivity / Q000517:prevention & control*; D006031:Glycosylation; D041943:Infant Formula / Q000737:chemistry*; D008239:Lysine / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D015416:Maillard Reaction; D010446:Peptide Fragments / Q000737:chemistry*
D000596:Amino Acids; D010446:Peptide Fragments; C018948:furosine; D008239:Lysine