Background:  Peanut allergen Ara h 3 has been the subject of investigation for the last few years. The reported data strongly depend on recombinant Ara h 3, since a purification protocol for Ara h 3 from peanuts was not available.

Methods:  Peanut allergen Ara h 3 (glycinin), was purified and its posttranslational processing was investigated. Its allergenic properties were determined by studying IgE binding characteristics of the purified protein.

Results:  Ara h 3 consists of a series of polypeptides ranging from approximately 14 to 45 kDa that can be classified as acidic and basic subunits, similar to the subunit organization of soy glycinin. N‐terminal sequences of the individual polypeptides were determined, and using the cDNA deduced amino‐acid sequence, the organization into subunits was explained by revealing posttranslational processing of the different polypeptides. IgE‐binding properties ofAra h 3 were investigated using direct elisa and Western blotting with sera from peanut‐allergic individuals. The basic subunits, and to a lesser extent the acidic subunits, bind IgE and may act as allergenic peptides.

Conclusions:  We conclude that peanut‐derived Ara h 3, in contrast to earlier reported recombinant Ara h 3, resembles, to a large extent, the molecular organization typical for proteins from the glycinin family. Furthermore, posttranslational processing of Ara h 3 affects the IgE‐binding properties and is therefore an essential subject of study for research on the allergenicity of Ara h 3.