Sensitivity to legumes is a prevalent food allergy in the Mediterranean area, with lentil and chickpea being the most frequent causes of allergic reactions. Most of the legume allergens identified are seed storage proteins, profilins, or pathogenesis-related proteins. However, allergenic proteins from chickpea have not been well characterized. This study presents the purification of an allergenic 11S globulin from chickpea.
Proteins were extracted from chickpea flour through a series of precipitation and centrifugation steps. Globulin fractions, containing 7S vicilins and 11S legumins, were further purified using ion exchange- and gel-filtration chromatography. The protein was analyzed by SDS-PAGE and LC-MS/MS. Sera from patients with known peanut, chickpea and/or lentil allergies were used to test for IgE reactivity using a chimeric IgE ELISA. Sequence homology was analyzed using BLASTp.
Chickpea 11S globulin consists of multiple polypeptides, which present as 20kD, 37kD, and 54kD bands on SDS-PAGE. All three polypeptides were identified as 11S seed storage protein by LC-MS/MS. Eight out of thirty six sera from patients allergic to peanut and/or lentils showed IgE reactivity against the purified globulin. The chickpea legumin amino acid sequence shares 53% identity and 72% homology with the major peanut allergen Ara h 3.
The purified chickpea allergen was confirmed to be an 11S globulin. Presence of multiple polypeptides indicates proteolytic processing characteristic for 11S plant storage proteins. Detection of IgE reactivity to chickpea legumin in sera from peanut and lentil allergic patients suggests that 11S globulins may be cross-reactive allergens of the legume family.