Glucoamylase: another fungal enzyme associated with baker's asthma

Abstract

Aspergillus-derived enzymes are widely used as dough additives in the baking industry. These enzymes may give rise to immunoglobulin (Ig)E-mediated sensitization and occupational asthma. Glucoamylase (or amyloglucosidase) is an important industrial enzyme obtained from Aspergillus niger and used to provide fermentable sugars for yeast to improve loaf volume and texture. The aim of our study was to investigate the potential allergenic role of glucoamylase in baker's asthma. We report four subjects with work-related allergic respiratory symptoms who were exposed to glucoamylase and other starch-cleaving enzymes used as baking additives. The causative role of glucoamylase in work-related asthma was investigated by immunologic tests and specific inhalation challenges (SIC). Glucoamylase allergenic components were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. Skin prick tests to glucoamylase (10 mg/mL) gave a positive response in all patients. Further, a positive skin prick test to alpha-amylase was obtained in the four patients and to hemicellulase in two of them. SIC to glucoamylase elicited isolated early asthmatic responses in the three patients tested, and SIC to alpha-amylase elicited early asthmatic responses in two patients and a dual asthmatic response in another patient. Immunoblotting with glucoamylase showed several IgE-binding bands with molecular masses between 33 and 96 kD. IgE-inhibition assays showed scarce to moderate allergenic cross-reactivity between glucoamylase and alpha-amylase. These bakers had developed IgE-mediated occupational asthma to glucoamylase and alpha-amylase. Fungal glucoamylase is widely used as a baking additive and this enzyme may give rise to allergic respiratory reactions among exposed workers.