HUMAN JEJUNAL TRANSGLUTAMINASE - DEMONSTRATION OF ACTIVITY, ENZYME-KINETICS AND SUBSTRATE-SPECIFICITY WITH SPECIAL RELATION TO GLIADIN AND CELIAC-DISEASE

Transglutaminase activity was demonstrated by radiometric assay for the 1st time in human jejunal mucosa. The activity was similar to that in other tissues, with a pH optimum of 9.0, an absolute requirement for Ca2+ and an apparent Km for putrescine of 0.15 mmol/l. Assay of jejunal transglutaminase activity with a variety of dietary proteins as acceptors showed high activity with gliadin, comparable with that of the standard substrate, dimethylcasein. Deamidation of the gliadin markedly reduced its acceptor activity. Collagen, ovalbumin, elastin and zein exhibited very low acceptor activities. Increased transglutaminase activity was demonstrated in jejunal biopsies from 4 patients with untreated celiac disease compared with inflammatory bowel disease. Eight patients with celiac disease in remission, with normal levels of brush border .alpha.-glucosidase, showed elevated transglutaminase activities compared with those of controls. Intestinal transglutaminase activity may be important in gliadin binding to tissues and thus in the pathogenesis of celiac disease.