k87 Asp o 21, alpha-amylase

Environmental Characteristics

Baker's asthma caused by flour dust exposure is a classic example of occupational asthma. To improve industrial processes and product quality, several non-cereal additives are today regularly present in baking flours. The starch-degrading enzyme alpha-amylase from Aspergillus oryzae and soybean flour (Glycine max) are examples of such additives that, together with the cereal components, are responsible for sensitization and IgE-mediated symptoms in bakers and others exposed to baking flours (1).

Clinical Relevance

Sensitization to enzymes in bakeries is a common cause of occupational asthma (2, 3) and may also result in contact dermatitis (4). The prevalence of sensitization to alpha-amylase in symptomatic bakers is about 25% (5, 6). Epidemiologic studies have shown that alpha-amylase exposure is strongly associated with enhanced risk of sensitization of bakery workers (7, 8). Bread made from flour containing alpha-amylase from Aspergillus oryzae can trigger allergic reactions in sensitized subjects (9, 10). Clinical reactions after ingestion of baked bread do not occur frequently in those sensitized to Aspergillus fumigatus (11).

Baker's asthma caused by flour dust exposure is a classic example of occupational asthma. To improve industrial processes and product quality, several non-cereal additives are today regularly present in baking flours. The starch-degrading enzyme alpha-amylase from Aspergillus oryzae and soybean flour (Glycine max) are examples of such additives, that together with the cereal components are responsible for sensitization and IgE-mediated symptoms in bakers and others exposed to baking flours (1). Sensitization to enzymes in bakeries is a common cause of occupational asthma (2, 3) and may also result in contact dermatitis (4). The prevalence of sensitization to alpha-amylase in symptomatic bakers is about 25% (5, 6). Epidemiologic studies have shown that alpha-amylase exposure is strongly associated with enhanced risk of sensitization of bakery workers (7, 8).

Work-related respiratory symptoms in small bakeries were significantly associated with specific IgE to alpha-amylase (12). In a study of 83 pharmaceutical-industry workers, sensitization was demonstrated in 26 workers by skin testing. Specific IgE antibodies were found in 24/26 of the workers with positive skin tests. No amylase-specific IgE antibodies were detected in non-exposed controls (13). Alpha-amylase hypersensitivity with positive skin tests and specific IgE antibodies was also observed in millers (14). Fungi naturally growing on stored cereal grains were assumed to be the source of the sensitization. This assumption is supported by the observation of common epitopes in amylase and extracts of Aspergillus oryzae (15).

The enzyme alpha-amylase, also referred to as allergen Asp o 2, loses its enzyme activity when heated. However, it has been shown to retain some allergenic activity even at 200° C (5, 16) and bread made from flour containing alpha -amylase from Aspergillus oryzae can trigger allergic reactions in sensitized subjects (9, 10). Clinical reactions after ingestion of baked bread do not occur frequently in those sensitized to Aspergillus fumigatus (11).

Molecular Aspects

Non-cereal additives such as the starch-degrading enzyme alpha-amylase from Aspergillus oryzae are today regularly present in baking flours.

Cross-reactivity

Alpha-amylase hypersensitivity with positive skin tests and specific IgE antibodies was also observed in millers (14). Fungi naturally growing on stored cereal grains were assumed to be the source of the sensitization. This assumption is supported by the observation of common epitopes in amylase and extracts of Aspergillus oryzae (15).

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Last reviewed: June 2022.