title: O-Methylisourea Can React with the α-Amino Group of Lysine: Implications for the Analysis of Reactive Lysine.
abstract: The specificity of O-methylisourea (OMIU) to bind to the ε-amino group of Lys, an important supposition for the OMIU-reactive Lys analysis of foods, feeds, ingredients, and digesta, was investigated. Crystalline l-Lys incubated under standard conditions with OMIU resulted in low homoarginine recoveries. The reaction of OMIU with the α-amino group of Lys was confirmed by MS analysis, with double derivatized Lys being identified. None of the changes in reaction conditions (OMIU pH, OMIU to Lys ratio, and reaction time) with crystalline l-Lys resulted in 100% recovery of homoarginine. The average free Lys content in ileal digesta of growing pigs and broilers was found to be 13% of total Lys, which could result in a significant underestimation of the reactive Lys content. The reaction of OMIU with α-amino groups may necessitate analysis of free Lys to accurately quantify reactive lysine in samples containing a large proportion of Lys with a free α-amino group.
authors.affiliation: Wageningen University & Research , Wageningen Livestock Research, P.O. Box 338, 6700 AH Wageningen, The Netherlands.|Wageningen University & Research , Animal Nutrition Group, P.O. Box 338, 6700 AH Wageningen, The Netherlands.
authors.forename: Tetske G
authors.identifier: http://orcid.org/0000-0003-2020-4281
authors.initials: TG
authors.lastname: Hulshof
authors.affiliation: Riddet Institute, Massey University , Private Bag 11222, Palmerston North, New Zealand.
authors.forename: Shane M
authors.initials: SM
authors.lastname: Rutherfurd
authors.affiliation: Laboratory of Food Chemistry, Wageningen University & Research , P.O. Box 17, 6700 AH, Wageningen, The Netherlands.|Department of Food Science, University of Parma , Parco Area delle Scienze 59/A, 43124 Parma, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Sforza
authors.affiliation: Wageningen University & Research , Wageningen Livestock Research, P.O. Box 338, 6700 AH Wageningen, The Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: Bikker
authors.affiliation: Wageningen University & Research , Animal Nutrition Group, P.O. Box 338, 6700 AH Wageningen, The Netherlands.
authors.forename: Antonius F B
authors.initials: AF
authors.lastname: van der Poel
authors.affiliation: Wageningen University & Research , Animal Nutrition Group, P.O. Box 338, 6700 AH Wageningen, The Netherlands.
authors.forename: Wouter H
authors.initials: WH
authors.lastname: Hendriks
mesh_terms: D000821:Animal Feed / Q000032:analysis; D000818:Animals; D002645:Chickens / Q000378:metabolism*; D004063:Digestion; D006709:Homoarginine / Q000737:chemistry / Q000378:metabolism; D008239:Lysine / Q000737:chemistry* / Q000378:metabolism; D008782:Methylurea Compounds / Q000737:chemistry* / Q000378:metabolism; D013552:Swine / Q000378:metabolism*
chemical_list: D008782:Methylurea Compounds; D006709:Homoarginine; C002249:O-methylisourea; D008239:Lysine
keywords: guanidination reaction; reaction conditions; reactive lysine; specificity