Nonpancreatic hydrolysis of N-benzoyl-L-tyrosyl-p-aminobenzoic acid (PABA peptide) in the rat small intestine.

Factors affecting the intestinal hydrolysis of orally administered N-benzoyl-L-tyrosyl-p-aminobenzoic acid (PABA peptide) and urinary recovery of p-aminobenzoic acid have been studied in rats, after diversion of the pancreatic and biliary secretions. The exclusion of pancreatic secretions from the small intestine lowered, but did not completely abolish, the urinary recovery of PABA, whereas diversion of the bile had no significant effect. A particulate-bound enzyme capable of splitting PABA peptide was found to be present throughout the rat small intestine, and its activity remained unchanged in the absence of biliopancreatic secretions. The intestinal PABA peptide hydrolase could be solubilized with papain and Triton from a partially purified brush-border membrane fraction, and it eluted in gel filtration as a high-molecular-weight peak, well separated from the other known peptidases of the intestinal brush-border membrane.