title: Oxidation of proline decreases immunoreactivity and alters structure of barley prolamin.
abstract: Elimination of celiac-toxic prolamin peptides and proteins is essential for Triticeae products to be gluten-free. Instead of enzymatic hydrolysis, in this study we investigated metal-catalyzed oxidation of two model peptides, QQPFP, and PQPQLPY, together with a hordein isolate from barley (Hordeum vulgare L.). We established a multiple reaction monitoring (MRM) LC-MS method to detect and quantify proline oxidation fragments. In addition to fragmentation, aggregation and side chain modifications were identified, including free thiol loss, carbonyl formation, and dityrosine formation. The immunoreactivity of the oxidized hordein isolate was considerably decreased in all metal-catalyzed oxidation systems. Cleavage of peptides or protein fragments at the numerous proline residues partially accounts for the decrease. Metal-catalyzed oxidation can thus be used in the modification and elimination of celiac-toxic peptides and proteins.
authors: Department of Food and Environmental Sciences, University of Helsinki, Agnes Sjöberginkatu 2, PL 66, Helsinki FI-00014, Finland. Electronic address: xin.huang@helsinki.fi.
authors: Xin
authors: X
authors: Huang
authors: Department of Food and Environmental Sciences, University of Helsinki, Agnes Sjöberginkatu 2, PL 66, Helsinki FI-00014, Finland.
authors: Tuula
authors: T
authors: Sontag-Strohm
authors: Department of Food and Environmental Sciences, University of Helsinki, Agnes Sjöberginkatu 2, PL 66, Helsinki FI-00014, Finland.
authors: Frederick L
authors: FL
authors: Stoddard
authors: School of Human Science and Environment, Research Institute for Food and Nutritional Sciences, University of Hyogo, Himeji, Hyogo 670-0092, Japan.
authors: Yoji
authors: Y
authors: Kato
mesh_terms: D005983:Glutens / Q000737:chemistry*; D001467:Hordeum / Q000737:chemistry*; D010084:Oxidation-Reduction; D011392:Proline / Q000737:chemistry*
chemical_list: D005983:Glutens; D011392:Proline
keywords: Barley; Gluten-free; Hordein; Metal-catalyzed oxidation; Prolamin; Proline; Proline oxidation