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ENZYMATIC AND CHEMICAL MODIFICATIONS OF FOOD ALLERGENS

In development of new methods for food allergen modification there are two main applications. First one, and the most frequent, is creation of hypoallergic food and food additives, and the second one is preparation of formulations for safe immunotherapy of food allergies. For both applications safety is obligatory, implicating usage of minimal toxic and nonalleregnic agents. Preferred reagents used for allergen modification are those acceptable for the production of foodstuffs or pharmaceuticals, and researches are more focused on usage of enzymes as modification agents, as well as compounds naturally occurring in food.

Chemical or enzymatic modification of allergen molecule may alter its structure or physically obstruct binding of IgE antibodies to conformational or linear epitopes. Reducing of alleregenicity can be achieved by removal of epitopes, destruction of epitopes, and by their masking. Modification can also lead to formation of insoluble complexes with allergens and thus decreasing soluble allergen content. Polymerisation of allergens can mask IgE antibody binding sites. Reducing of allergenic properties by chemical or enzymatic methods was demonstrated on full extract, raw or pretreated, or on isolated allergens from peanut, wheat, whey, soy, pea and cherry.

Covalent and noncovalent chemical modifications of food allergens for reducing their allergenicity were invstigated. Covalent modifications can be achieved by acylation, carbamoylation, nitration, polymerization by glutaraldehyde, covalent hydrophilisation by conjugation with polysaccharides and covalent lipophilization by conjugation with fatty acids. Also, modifications by oxidation in presence of heavy metal ions (Cu2+, Fe 2+, etc.) with hydrogen peroxide, or reduction with 2-mercaptoethanol, dithiothreitol, cysteine, glutathione, etc., or by using proteins glutaredoxin or thioredoxin. Noncovalent modifications with phytic acid, phenolic compounds, polysaccharides and oxidized lipids have shown to be effective.

The most frequent used enzymes for reducing food allergenicity are proteases leading to various degrees of allergen fragmentation resulting in different hypoallergenic hydrolysates available on the market. Enzymatic cross-linking of proteins, by transglutaminases, peroxisases and phenol oxidases (such as tyrosinases and laccases), is currently exploited in the food processing industry. However, as enzymes themselves are proteins their introduction into foods may carry a risk of eliciting an allergic response in patients sensitive to the enzyme in question or to related proteins.

It seems that the most effective approach for allergen modification is combination of two or more methods acting by different mechanisms, such as combination of acylation and proteolysis, reduction, alkylation and cross-linking, cross-linking and reduction, proteolysis and cross-linking). In the future chemical and enzymatic methods for modification of food allergen have potential in development of safe preparations for immunotherapy of food allergies as well.

Dr Olga Vuckovic Dr. Dragana Stanić-Vučinić,
Senior Research Scientist
Faculty of Chemistry University of Belgrade
Belgrade, Serbia

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