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Cellulose esters of both alkyl and aryl carboxylic acids have been prepared and tested as noncovalent adsorbents for enzymes. Phenoxyacetyl cellulose strongly bound all 10 of the enzymes tested. The bound enzymes, which were not desorbed by 1 m (NH4)2SO4 or moderate (25–50%) concentrations of nonaqueous solvents but which were at least partially desorbed by solutions containing nonionic detergents, usually exhibited nearly complete retention of catalytic activity. Other materials, paper, string, cotton, and glass beads, have been analogously derivatized with similar results. This simple and effective technique warrants consideration for applications in enzyme immobilization.

Antigliadin antibodies (AGA) were analyzed by immunoblotting from the sera of 30 patients with dermatitis herpetiformis (DH) and of 13 patients with gluten-sensitive enteropathy (GSE). The results were correlated to the jejunal morphology and to the serum AGA values as quantified with an enzyme-linked immunosorbent assay (ELISA). Immunoblotting analysis disclosed a distinct pattern of AGA which was similar in patients with DH and GSE. In both diseases individual variation in IgG class AGA patterns was large, suggesting that several antigenic determinants are involved in the AGA response. The IgA class AGA pattern was clearly more homogeneous. The sera with several bands in immunoblotting had the highest AGA levels in ELISA. Strong staining in the main gliadin area (bands from 31 to 38 kd) indicated severely damaged intestinal mucosa whereas the serum of DH patients with partial villous atrophy or normal mucosa showed usually weaker staining. The immunoblotting pattern of sera from healthy controls was even weaker but was directed against the same polypeptides as in the patients suggesting a quantitative rather than qualitative difference between healthy and diseased subjects. This difference was, however, more obvious in the IgA than in the IgG class AGA pattern possibly indicating a more fundamental defect in the regulation of synthesis of IgA isotype in DH and GSE.

131I-insulin was given intravenously to normal rats, and the passage of radioactivity into the duodenal loop containing a proteasis inhibitor was studied by two techniques. In the first, the 131I-insulin was separated from the intestinal content by electrophoresis; whereas in the second, the radioactivity that remained on an ion-exchange resin, directly introduced into the small intestine, was measured. It was found that within 15 minutes from the injection a small amount of 131I-insulin passes into the gut lumen. — The absorption of 131I-insulin from small intestine into the blood was studied after introduction of 131I-insulin along with a proteasis inhibitor into the intestinal loop. The autoradiograph of the electrophoresis of serum showed plasma-protein-bound radioactivity but no radioactivity due to unbound (free) insulin-131I. — These findings show that the passage of insulin through the intestinal wall of rats can be demonstrated by neutralizing the proteolytic activity in the intestinal tract. The possible role of this passage in protein-losing enteropathy is pointed out.

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. Our finding that intestinal alkaline phosphatase activity tended to parallel imidopeptide hydrolase activity, and that activity (a) was partially localized to the particulate fraction of mucosal homogenate, suggested that imidopeptide hydrolase activities may be located in the microvilli of the intestinal epithelium and that, like alkaline phosphatase activity, they may be reduced in flattened mucosae, in part at least because of the pathologic changes in the microvilli. In our studies of control subjects we did not detect peptide hydrolase activity deficiency analogous to asymptomatic disaccharidase deficiency.