Peptide hydrolase activities of the mucosa of human small intestine

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Abstract

Few studies have been published on peptide hydrolase activities of human small intestine mucosa. We developed methods to screen tissue extracts for such enzymes and to quantitate hydrolase activities for dipeptides containing the aromatic amino acid L-phenylalanine. The screening procedure indicated glycyl-L-proline hydrolase activity was reduced in biopsy specimens from patients with flattened intestinal mucosa. To explore this further, we established optimal assay conditions for hydrolase activities (a) glycyl-L-proline, (b) L-phenylalanyl-L-proline, (c) L-alanyl-L-phenylalanine, and (d) L-phenylalanylglycine. Biopsy specimens from patients with various intestinal disorders, but without flattened mucosa, and from three patients with flattened mucosa, showed a disproportionate reduction in activities (a) and (b), with the reduction being significantly more marked in the latter patients. We suggest that intestinal imidopeptide hydrolase activities, such as (a) and (b), are sensitive to changes in intestinal disease generally, particularly to the altered physiology associated with flattening of the mucosa, and are secondary to, rather than a cause of, the intestinal pathology.

Authors

William D. Heizer, Leonard Laster