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Abstract
In this study, we investigated the presystemic metabolism of trypsin and bromelain and the influence of these proteolytic enzymes on the mucus layer covering the gastrointestinal (GI) epithelia. In vitro studies demonstrated that 77.3% ± 4.0% (mean ± SD, n = 3) of trypsin is autodegraded within 2 hr, whereas autodegradation of bromelain was negligible. In contrast to the metabolization of bromelain by all pancreatic serine proteases, trypsin is only degraded to some extent by elastase. Both therapeutically used enzymes remained stable after incubation with an excised porcine mucosa, demonstrating that proteolysis caused by brush border membrane–bound enzymes is negligible. Trypsin and bromelain were highly mucolytic active, thereby reducing the diffusion barrier based on the mucus gel layer. Strategies to improve the galenic of dosage forms for trypsin and bromelain include the use of bioadhesive polymers such as hydroxyethylcellulose or slightly modified chitosan-EDTA, providing strongly improved stability of these enzymes toward proteolytic degradation in vitro. The given information represents a good starting point to improve the galenic of dosage forms for orally administered proteolytic enzymes.