Peanut allergy is one of the most severe food allergies. One effort to alleviate this problem is to identify peanut germplasm with lower levels of allergens which could be used in conventional breeding to produce a less allergenic peanut cultivar. In this study, we identified one peanut line, GT-C9, lacking several seed proteins, which were identified as Ara h 3 isoforms by peptide sequencing and named iso-Ara h 3. Total seed proteins were analyzed by one-dimensional (SDS-PAGE) and two-dimensional gel electrophoreses (2-D PAGE). The total protein extracts were also tested for levels of protein-bound end products or adducts such as advanced glycation end products (AGE) and N-(carboxymethyl) lysine (CML), and IgE binding. Peanut genotypes of GT-C9 and GT-C20 exhibited significantly lower levels of AGE adducts and of IgE binding. This potential peanut allergen iso-Ara h 3 was confirmed by peptide sequences and Western blot analysis using specific anti-Ara h 1, Ara h 2, and Ara h 3 antibodies. A full-length sequence of iso-ara h 3 (GenBank number DQ855115) was obtained. The deduced amino acid sequence iso-Ara h 3 (ABI17154) has the first three of four IgE-binding epitopes of Ara h 3. Anti-Ara h 3 antibodies reacted with two groups of protein peptides, one with strong reactions and another with weak reactions. These peptide spots with weak reaction on 2-D PAGE to anti-Ara h 3 antibodies are subunits or isoallergens of this potential peanut allergen iso-Ara h 3. A recent study suggested that Ara h 3 basic subunits may be more significant allergenicity than the acidic subunits.

Peanuts are complex storage proteins with high contents and have been identified as one of the most allergenic foods. In this review, we summarize some of the latest findings and the potential importance of the Ara h 3 basic subunit, which has been overlooked as an allergen in early literature. Some recent studies indicate that Ara h 3 basic subunit may be as significant as or even a more important allergen than the acidic subunit. For example, one clinical study found a group of children with peanut allergy who were specifically sensitized to the basic subunit of Ara h 3. Although, proteomic analysis of total peanut storage proteins has revealed limited polymorphic profiles of major proteins in diverse peanut germplasm accessions, a study reported a peanut breeding line 'GT-C9' lacking several seed protein peptides, in which the missed major proteins were basic subunits of Ara h 3. This breeding line was shown to exhibit significantly lower levels of advanced glycation end (AGE) products and IgE binding by the sera of peanut allergic patients, which implies a role for the basic subunit of Ara h 3 in the allergenicity of peanuts. Further studies are needed to investigate the contribution of Ara h 3 basic subunits to peanut allergenicity.