Inhibition of proteolysis in luminal extracts from the intestine of the brushtail possum

The proteolytic activity of luminal extracts from five regions (duodenum, jejunum, ileum, caecum and colon) of the brushtail possum intestine towards bovine serum albumin (BSA) and human luteinizing hormone releasing hormone (LHRH) was investigated. There were no significant differences in degradation rates between fresh and previously frozen extracts from any region of the possum intestine. The inhibition of degradation of BSA by luminal extracts from two regions (jejunum and ileum) and of LHRH from four regions (jejunum, ileum, caecum and colon) was evaluated. Soybean trypsin‐chymotrypsin inhibitor (SBTI), sodium deoxycholate, Carbopol 934P, bacitracin and bestatin significantly inhibited the degradation of both LHRH and BSA (P < 0.05). SBTI almost totally inhibited the proteolysis of BSA and the peptidolysis of LHRH in extracts from the small intestine. This finding suggests that serine proteases such as chymotrypsin are responsible for the protein and peptide degradation in luminal extracts. It is concluded that including serine protease inhibitors in a formulation may enhance oral delivery of bioactive peptides and proteins to possums.