Proteolytic enzymes of human intestinal mucosa in non-malignant diseases of the ileum and colon.

Preparations of mucosal epithelium were made from 10 samples of normal colon, 10 of normal ileum, 20 from colon involved by ulcerative colitis, 10 from ileum affected by regional ileitis, 4 from colon resected for diverticulitis, 2 from megacolon, and 2 from colonic polyps. The activity of proteolytic enzymes using haemoglobin as substrate and tissue nitrogen as reference was measured at pH 3·75 and pH 6·50 in homogenates, supernatants and particulate preparations before and after treatment with detergent. In normal colon and ileum, proteolytic activity at pH 3·75 was of similar magnitude and was mainly soluble; activity at pH 6·50 was greater in ileum, and in both tissues was mainly associated with particulate fractions. Samples involved by ulcerative colitis gave lower activities in all fractions at both pH values, the extent of the reduction being related to the severity of the disease. No evidence for a lysosomal defect was obtained. Samples affected by regional ileitis did not differ from normal ileum in proteolytic activity at pH 3·75, but values at pH 6·50 tended to be lower. At both pH values, a higher percentage of the total activity was soluble prior to treatment with detergent which solubilised little additional enzyme; this may indicate a lysosomal defect. Diverticulitis samples had lower activity at pH 3·75, but did not differ from normal colon at pH 6·50. No striking abnormalities were noted in megacolon or colonic polyps.