Distribution of brush-border membrane peptidases along the rabbit intestine: implication for oral delivery of peptide drugs.

The distribution profiles of brush border membrane activities of endopeptidase-24.11, angiotensin converting enzyme (ACE), and dipeptidyl peptidase IV (DPP IV) along the rabbit intestine were examined. DPP IV had the lowest activity in the duodenum and much higher in other segments. In those segments, its activities were similar. As regards endopeptidase-24.11 and ACE, the jejunum had the highest activities, followed by the duodenum and the ileum. Activities of these two enzymes were lower in the distal intestine. The decline of ACE activity toward the distal end was more dramatic than that of endopeptidase-24.11 activity. The results suggest that, along the intestine, endopeptidase-24.11 and ACE have similar distribution profiles while DPP IV has a different distribution pattern.