No abstract

The effect of baking and digestion on the allergenicity of wheat flour proteins has been studied. Pooled sera of patients suffering from food allergy to wheat products were tested for IgE binding to the proteins of the wheat dough and of the bread crumb and crust, before and after being in vitro digested. During in vitro digestion, the IgE binding protein components of the unheated dough tended to disappear, whereas a permanence of IgE recognition was evident for both the bread crumb and crust. This indicates that the baking process increases the resistance of the potential allergens of the wheat flour to proteolytic digestion, allowing them to reach the gastrointestinal tract, where they can elicit the immunological response. Therefore, the effects of baking must be carefully considered in studying food allergies to wheat products.

For the atopic patients the positivity to skin prick test and CAP to wheat was in accordance with the immunoblotting results and a food allergy to wheat could be diagnosed. In these patients a major allergen was a 16-kDa band corresponding to members of the cereal alpha-amylase/trypsin inhibitors protein family, the major allergens involved in baker's asthma. In the non-atopic patients the positive immunoblotting results contrasted with the responses of the allergologic tests, indicating that the allergenic wheat protein preparations currently used are of limited value in detecting specific IgE to wheat and that the fraction of irritable bowel syndrome (IBS) patients with food allergy may be larger than believed.

Thylakoids from enzymatically separated bundle sheath and mesophyll tissue chloroplasts were examined for their chlorophyll‐proteins by tube sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS‐PAGE). Differences were found in distribution of chlorophyll among peaks. The chlorophyll‐protein a peak (CPa), considered to be the photosystem II (PSII) reaction centre by many authors, was seen to be absent in bundle sheath thylakoid samples. The slab SDS‐PAGE revealed the absence of the polypeptides present in PSII preparations of chloroplast subfractions having only PSII activity. This finding confirms Anderson's hypothesis of the structure of grana and stroma thylakoids.

SDS-PAGE analysis revealed that what was considered the major protein of beer is actually formed by two polypeptides with the same molecular mass (-40 kDa), but different hydrodynamic volumes in their incompletely unfolded conformation. The two polypeptides share common properties, although the one with the more open conformation is associated with sugars, whereas the other is not. Immunoblotting experiments with polyclonal antibodies raised against the two electrophoretically purified polypeptides indicated that they are immunologically related and allowed the identification of their precursors in barley grain. These latter are two heat-resistant albumins whose electrophoretic behavior corresponded to that of beer proteins. These two albumins coincide with protein Z, the first member of the serpin superfamily described in plants.