METABOLISM OF GLYCOSYL UREIDES BY HUMAN INTESTINAL BRUSH-BORDER ENZYMES

C-13-labeled glycosyl ureides were recently proposed as a new marker o f the orocecal transit time: after passing the small bowel the sugar-u rea bond is split by bacterial allantoicase. Further degradation resul ts in (CO2)-C-13 which can be measured in the exhaled breath. The aim of this study was to detect an eventual allantoicase-like activity in the human gut and to elucidate the metabolism of glycosyl ureides by h uman intestinal brush border enzymes. Biopsies of 15 duodenal specimen and 6 colon specimen were homogenised and incubated with several disa ccharides and their corresponding disaccharide ureides under various e xperimental conditions. Hydrolysis of the sugar-urea bond could not be observed neither in the small bowel nor in the colon. However, the co njugation between the two sugars was split. In a modified Dahlqvist as say lactase showed the same kinetics with lactose and lactose ureide a s substrates whereas maltose showed a significantly 2.6-fold higher af finity to maltase than maltose ureide (P < 0.001). No major difference between these two substrates could be detected when total maltase act ivity was inhibited by acarbose. In summary, the human gut tissue poss esses no allantoicase-like activity. Therefore, glycosyl ureides seem to be appropriate substances to test the orocecal transit time. (C) 19 97 Elsevier Science B.V.