Caricain: A basis for enzyme therapy for coeliac disease

Abstract

Gliadin, a glycoprotein present in wheat and other grass cereals, is a causative agent in coeliac disease. It is therefore important to find methods for the detoxification of gliadin. Lysosomal integrity is lost in patients with active coeliac disease but restored when gliadin is removed from the diet. We employed a rat liver lysosome assay to monitor the extent of detoxification of a gliadin digest by caricain, a protein enzyme found in papaya. Pre-incubating the gliadin digest for different durations with caricain allowed the kinetics of the detoxification process to be studied. A significant degree of protection (80%) of the lysosomes was achieved with 1.7% w/w of caricain on substrate after incubation for 2 h at 37 °C. The detoxification followed first-order kinetics with a rate constant of 1.7 x 10^-4/s. The enzyme was strongly inhibited by imidazole, but weakly by phenylmethyl sulphonyl fluoride, as was also a caricain-enriched fraction from ion-exchange chromatography of papaya oleo-resin. The value of caricain in the detoxification of gliadin was confirmed in the present studies and this enzyme shows promise for enzyme therapy in coeliac disease.