Degradation of C-hordein by metal-catalysed oxidation

Johnson

Journal of Cereal Science

et al. 2016

To improve the rheological properties of zein doughs, α-type zein and zein-starch doughs were prepared with the oxidising agents, hydrogen peroxide and peroxidase, which strengthen gluten-based doughs by cross-linking. Hydrogen peroxide and peroxidase increased zein dough extensibility compared to preparation with water. Hydrogen peroxide prepared zein doughs were extensible and cohesive below zein's glass transition temperature.The doughs did not exude water and maintained flexibility when stored. Confocal laser scanning microscopy revealed that in zein-starch doughs prepared with hydrogen peroxide a thin continuous zein matrix was formed around the starch granules, whereas doughs prepared with water exhibited clumps of granules. SDS-PAGE of zein doughs and films treated with the oxidising agents showed no evidence of zein polymerisation, nor did Fourier transform infrared spectrometry reveal any significant changes in secondary structure. Further, hydrogen peroxide treatment did not increase zein film glass transition temperature, but it did increase transition enthalpy, and film water uptake increased with hydrogen peroxide concentration. The greatly increased extensibility of hydrogen peroxide prepared zein doughs and their improved water-holding are not due to oxidative cross-linking. It is proposed that the effects are primarily due to hydroxylation of amino acid aliphatic side chains, improving hydration through hydrogen bonding.2

Section: Discussionmentioning

confidence: 99%

“…Tyrosinase was found to cross-link isolated oat globulins but not oat prolamins (Flander et al, 2011). Recently, it has been shown the barley C-hordein can be degraded and undergo side-chain modification through treatment with metal catalysed hydrogen peroxide induced oxidation (Huang et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Oxidation of commercial (α-type) zein with hydrogen peroxide improves its hydration and dramatically increases dough extensibility even below its glass transition temperature

Johnson

Journal of Cereal Science

et al. 2016

“…The size distribution of the oxidized mixture was analyzed with two connected columns, Superdex peptide 10/300 GL and Superdex 200 10/300 GL (GE Healthcare Biosciences, Uppsala, Sweden) as described previously (Huang et al, 2016).…”

Section: Size-exclusion Chromatography Of Hordein Oxidationmentioning

confidence: 99%

“…Proteolytic enzymes, such as proteases from seed germination (Loponen, Kanerva, Zhang, Sontag-Strohm, Salovaara & Gänzle, 2009) and proline-endopeptidase (Luoto et al, 2012) may be used for prolamin degradation. We have previously demonstrated that metal-catalyzed oxidation degraded a model celiac peptide 33-mer (Huang, Kanerva, Salovaara, Loponen & Sontag-Strohm, 2013) and C-hordein (Huang, Kanerva, Salovaara & Sontag-Strohm, 2016), as shown by substantial reductions in the immunoreactivity of both substrates in R5-based enzyme-linked immunosorbent assay (ELISA). Protein degradation and aggregation both occurred during oxidation, and oxidation of proline residues could partially explain this phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Oxidation of proline decreases immunoreactivity and alters structure of barley prolamin

et al. 2017

Self Cite

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.

“…() reported ‘gluten concentrations’ as high as 20% in wheat, which suggests that such high response in reactivity of epitopes is unlikely to match gluten weight. The use of R5 ELISA in barley analysis has also been reported to cause a large overestimation of hordeins because the number of epitopes in hordeins that R5 can recognise was higher than in the wheat gliadin reference material (Huang et al ., ). Our data suggest that the response of epitopes towards R5 monoclonal antibodies varies according to wheat type, being higher for hexaploids than tetraploids.…”

Section: Discussionmentioning

confidence: 92%

Gluten weight in ancient and modern wheat and the reactivity of epitopes towards R5 and G12 monoclonal antibodies

Gélinas

McKinnon

2016

Int J of Food Sci Tech

Differences in the level of coeliac-active gluten epitopes in wheat might have some significance for individuals reporting noncoeliac gluten sensitivity. The aim of this study was to compare the reactivity of epitopes towards ELISA R5 and G12 monoclonal antibodies in ancient (emmer; Khorasan wheat; spelt) and modern wheat (common bread wheat; durum), and to check whether the bread-making process leads to the degradation of epitopes. Data from ELISA R5 and G12 did not match gluten dry weight in wheat. Bread dough fermentation and extensive baking did not change the reactivity of coeliac-active epitopes towards monoclonal antibodies. Compared to hexaploid bread-type wheat (spelt; common bread wheat), ancient and modern pasta-type tetraploid wheat (emmer; Khorasan; durum) had less epitopes reactive towards ELISA R5 and G12 and might be preferable for wheat-sensitive individuals looking for food with reduced coeliac-active epitopes.