Distinct Fecal Proteolytic Activity in Zoo Animals with Different Feeding Strategies

Impaired intestinal proteolytic activity can lead to increased intestinal permeability. Differences in dietary protein intake may influence proteolytic activity in the digestive system. This study investigated whether intestinal proteolytic activity can be influenced by diet. Fecal samples from representative species of each different dietary group—carnivore, herbivore, and omnivore—were analyzed using fluorescence resonance energy transfer (FRET) peptide substrates to measure enzyme activity. Specific protease inhibitors were applied to identify the enzyme classes responsible for substrate degradation. Results showed that total proteolytic activity was significantly higher in feces from carnivores and omnivores than in those of herbivores. The addition of a serine protease inhibitor substantially reduced substrate degradation, indicating that serine proteases accounted for most of the observed activity. These findings demonstrate that proteolytic activity in feces is closely related to dietary protein intake and suggest that the regulation of proteases in the digestive tract may be influenced by feeding behavior and nutritional requirements.