[Activity of enkephalinase (EC.3.4.24.11). Neutral endopeptidase (NEP)in human digestive tract epithelial cells]

The activity was studied of enkephalinase (endopeptidase 24.11, neutral endopeptidase)--a membrane enzyme of epithelial cells within human digestive tract (in the stomach, duodenum, small intestine, ascending, descending and sigmoid colon, and rectum). The enzyme activity was determined by column method using the labelled substrate (H-D-AlaLeu)--enkephalin and the selective enkephalin inhibitor--thiorfan in the presence of bestatin and captopril--inhibitors of aminopeptidases and angiotensin converting enzyme respectively. The highest enkephalinase activity was found in the duodenal epithelium (77.3 8.0 fmol of the substrate/min/mg of protein) and in the small intestine (23.4 0.9 fmol/min/mg of protein) with its gradual decrease when progressing down the gastrointestinal tract. This result confirms the hypothesis of enkephalinase participation in protein hydrolysis processes.