Relative and Absolute Quantitation of Ten Allergens in Twenty Commercial Soybean Varieties Using Tandem Mass Spectrometry

RATIONALE: Some of the proteins expressed in the soybean (Glycine max) seed are allergenic to humans and animals; however, the concentration of these allergens and their variability in expression across germplasms is presently unknown.METHODS: Ten allergens were quantified from twenty non-genetically modified commercial soybean varieties using two parallel, label-free mass spectrometry approaches. Relative quantitation was performed by spectral counting and absolute quantitation was performed using multiple reaction monitoring (MRM) with synthetic, isotope-labeled peptides as internal standards.RESULTS: In the relative quantitation analysis, ten target allergens were identified; and five of these allergens showed concentration levels higher than the technical variation observed for the bovine serum albumin (BSA) internal standard (∼11%), suggesting concentration differences among the varieties. To confirm this observation, absolute quantitation of these allergens from each variety was performed; and the concentrations of eight of the ten allergens in seed ranged from approximately 0.5 to 5.7 μg/mg of soy extract. MRM analysis reduced the technical variance of the BSA internal standard to approximately 7%, and confirmed differential concentrations for four allergens across the twenty varieties.CONCLUSIONS: This is the first quantitative assessment of its kind for a majority of the known soybean allergens and the data, taken together, show that while concentrations of individual allergens varied, the total concentration of allergens among the soy varieties was similar. RATIONALE: Some of the proteins expressed in the soybean (Glycine max) seed are allergenic to humans and animals; however, the concentration of these allergens and their variability in expression across germplasms is presently unknown. METHODS: Ten allergens were quantified from twenty non-genetically modified commercial soybean varieties using two parallel, label-free mass spectrometry approaches. Relative quantitation was performed by spectral counting and absolute quantitation was performed using multiple reaction monitoring (MRM) with synthetic, isotope-labeled peptides as internal standards. RESULTS: In the relative quantitation analysis, ten target allergens were identified; and five of these allergens showed concentration levels higher than the technical variation observed for the bovine serum albumin (BSA) internal standard (∼11%), suggesting concentration differences among the varieties. To confirm this observation, absolute quantitation of these allergens from each variety was performed; and the concentrations of eight of the ten allergens in seed ranged from approximately 0.5 to 5.7 μg/mg of soy extract. MRM analysis reduced the technical variance of the BSA internal standard to approximately 7%, and confirmed differential concentrations for four allergens across the twenty varieties. CONCLUSIONS: This is the first quantitative assessment of its kind for a majority of the known soybean allergens and the data, taken together, show that while concentrations of individual allergens varied, the total concentration of allergens among the soy varieties was similar.