Identification of Peanut Agglutinin and Soybean Trypsin Inhibitor as Minor Legume Allergens

Abstract

Peanuts and soybeans are frequent causes of food hypersensitivity reactions in children. Sera from 12 patients with atopic dermatitis and a positive double-blind placebo-controlled food challenge to peanut and sera from 5 patients with atopic dermatitis and a positive double-blind placebo-controlled food challenge to soybean were used to identify and characterize specific legume allergens. Identification of a minor allergen from peanut and a minor allergen from soybean was accomplished using various physicochemical techniques. The peanut fraction, peanut agglutinin, isolated by anion-exchange chromatography and electrolution and confirmed by amino acid sequencing, bound IgE in only 50% of the peanut challenge positive patients. The soybean fraction, soybean trypsin inhibitor, identified by gel filtration and electroelution and confirmed by amino acid sequencing, bound IgE in only 20% of the soy challenge positive patients. The identification of these two known legume proteins as minor allergens should allow further immunologic and structural investigations to compare the major and minor legume allergens.

C-Terminal 23�kDa polypeptide of soybean Gly�m�Bd 28�K is a potential allergen

“…This C-terminal polypeptide derived from Gly m Bd 28 K has a predicted size of 23 kDa and a predicted pI of 5.62, which will place it in a region where several abundant soybean proteins and allergens, such as the soybean Kunitz trypsin inhibitor and the basic chains of the glycinins (Burks et al 1994;Helm et al 2000aHelm et al , 2000b, would normally migrate in 1-and 2-D gels. This may have precluded its prior identification as an IgE-binding protein in soy extracts and would make its present direct identification in soybean extracts quite challenging.…”

Stability of the allergenic soybean Kunitz trypsin inhibitor

“…SKTI has been established as a minor component in the array of soy allergenic proteins based on IgE binding, skin prick tests and SGF proteolysis [2,3]. The beta-sheet structure of SKTI is shared with other allergens, consistent with its allergenic potential [25,26].…”

“…This 21.5 kDa non-glycosylated protein was first isolated and crystallized from soybean seeds by Kunitz [1]. It has been characterized as a food allergen in humans consuming soy proteins [2,3]. In addition to its presence in foods prepared with whole soybeans, SKTI is found as a contaminant in lecithin [4], a phospholipid product widely used in foods and pharmaceuticals as an emulsifier.…”

Molecular Properties of Plant Food Allergens: A Current Classification into Protein Families

“…Regarding allergenicity, the most prominent member of this group is the soybean trypsin inhibitor. Although only 20% of soybean-allergic patients react with this soybean allergen, food induced anaphylactic shocks have been reported [76,77]. In addition to its presence in soy, the soybean trypsin inhibitor is also found as a contaminant in lecithin [78], which is widely used as emulgating agent and represents a potential risk for allergic patients.…”