Deglycosylation of ovalbumin prohibits formation of a heat‐stable conformer

Abstract

To study the influence of the carbohydrate-moiety of ovalbumin on the formation of the heat-stable conformer S-ovalbumin, ovalbumin is deglycosylated with PNGase-F under native conditions. Although the enzymatic deglycosylation procedure resulted in a complete loss of the ability to bind to Concavalin A column-material, only in about 50% the proteins lost their complete carbohydrate moiety, as demonstrated by mass spectrometry and size exclusion chromatography. Thermal stability and conformational changes were determined using circular dichroism and differential scanning calorimetry and demonstrated at ambient temperature no conformational changes due to the deglycosylation. Also the denaturation temperature of the processed proteins remained the same (77.4 +/- 0.4 degrees C). After heat treatment of the processed protein at 55 degrees C and pH 9.9 for 72 h, the condition that converts native ovalbumin into the heat-stable conformer (S-ovalbumin), only the material with the intact carbohydrate moiety forms this heat-stable conformer. The material that effectively lost its carbohydrate moiety appeared fully denatured and aggregated due to these processing conditions. These results indicate that the PNGase-F treatment of ovalbumin prohibits the formation and stabilization of the heat-stable conformer S-ovalbumin. Since S-ovalbumin in egg protein samples is known to affect functional properties, this work illustrates a potential route to control the quality of egg protein ingredients.

Keratinocyte-Releasable Factors Stimulate the Expression of Granulocyte Colony-Stimulating Factor in Human Dermal Fibroblasts

“…Similar processes have been described in the context of heat shock proteins and HIF‐1α stabilization intracellularly [Trisciuoglio et al, ]. In a related fashion, other cytokines have been shown to rest in dormant states, extracellularly bound to matrix components and glycoproteins that are cleaved following trauma [de Groot et al, ; Axelsson et al, ]. In this case, the trauma of heat treatment may denature any bound components while preserving active sites on IL‐1 or other G‐CSF‐stimulating factors.…”

Estimation of egg freshness using S-ovalbumin as an indicator

“…Spectroscopic studies indicated that the conformational change is very limited and involves a small alteration in the secondary structure, without a major alteration in the overall folding of the protein (Huntington et al, 1995;de Groot et al, 2007). Because ovalbumin is transformed into S-ovalbumin irreversibly during prolonged storage of shelled eggs and the formation velocity is only affected by pH and temperature, it was chosen as the reference index to express the freshness of the commercial shell eggs in the equivalent age (Smith and Back, 1965;Masaaki, 2005;de Groot et al, 2007).…”

Specific Isolation of Glycoproteins with Mesoporous Zirconia‐Polyoxometalate Hybrid

“…At the same time, the adsorption efficiencies of glycoproteins were much higher than those of non‐glycoproteins, and the adsorption efficiencies of Ova, IgG, γ‐Glo, and ConA increased gradually as the NaCl concentration increased. Ova has a solvent‐exposed carbohydrate chain containing four to six mannose residues and two to four N ‐acetyl‐β‐ d ‐glucosamine residues, and the surface of HRP is neutral under tested pH conditions; therefore, the hydroxyl groups of these two glycoproteins were exposed and the adsorption efficiencies were largely unaffected by the ionic strength. The sugar moiety of IgG consisting of 30 different bi‐antennary glycan structures is buried within the hydrophobic core between two constant fragments .…”