Abstract
ABSTRACTThis study investigated the effects of enzymatic deglycosylation following ultrasound pretreatment on structure and immunoreactivity of soybean 7S globulin. Soybean 7S globulin was pretreated by ultrasound (40 kHz, 300 W) and enzymatically deglycosylated by peptide-N-glycosidase F (PNGase F). Changes in structure of processed soybean 7S globulin were characterized by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, reversed-phase high-performance liquid chromatography, ultraviolet absorption spectrum, circular dichroism spectrum, and surface hydrophobicity analysis. Enzyme-linked immunoabsorbent assay was used to evaluate IgE-binding ability. The results showed that the glycan moieties of soybean 7S globulin were effectively removed by PNGase F, which significantly modified protein structures including the secondary and tertiary structures of 7S globulin. Individual enzymatic deglycosylation could reduce IgE-binding capacity of 7S globulin, whereas enzymatic deglycosylation following ultrasound pretreatment enhanced its IgE-binding capacity. In conclusion, soybean 7S globulin treated by single enzymatic deglycosylation can reduce potential allergenicity and may be employed in hypoallergenic food preparation.
Highlights
Soybean is widely used in the food industry for its nutritional value and desirable functional properties.[1]
Soybean 7S globulin is a glycoprotein and one of the most important allergens. βconglycinin (140–170 kDa) is major component of 7S globulin, which consists of three subunits, namely, α (~67 kDa), α′ (~71 kDa), and β (~50 kDa) subunits. α subunit is defined as Gly m Bd 60K.[5]
Bands with similar molecular mass were exhibited, but slight reduction in molecular weight of polypeptide of β-conglycinin and higher electrophoretic mobility were observed in lane of 7S globulin treated with enzymatic deglycosylation compared with the native 7S globulin
Summary
Soybean is widely used in the food industry for its nutritional value and desirable functional properties.[1]. Α subunit is defined as Gly m Bd 60K.[5] β-conglycinin is a glycoprotein containing 4–5% of carbohydrate moieties, which are N-linked to polypeptide chains.[6] Gly m Bd 30K (34 kDa), which consists of 258 amino acid residues, is another glycoprotein contained in disulphide linkages of 7S globulin.[7] A study reported that Gly m Bd 28K (26 kDa) is a glycoprotein-bearing xylosyl residue and can bind with IgE from soybeansensitive patients.[8] Currently, 38 kinds of soybean allergens are known, and three of them, including Gly m Bd 60K, Gly m Bd 30K, and Gly m Bd 28K exist in 7S globulin; these three molecules are major allergens found in soybeans.[9]
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