1. α1-Proteinase inhibitor (α1-antitrypsin) is excreted in a deglycosylated form (Mr 38000) in the faeces of healthy subjects and in patients with quiescent Crohn's disease. By contrast, in most patients with active Crohn's disease, α1-proteinase inhibitor is excreted in a glycosylated form (Mr 51000).
2. Faecal extracts containing deglycosylated α1-proteinase inhibitor are able to deglycosylate α1-proteinase inhibitor by an exoglycosidic process. Conversely, we demonstrate that in faecal extracts from patients excreting glycosylated α1-proteinase inhibitor, glycosidase activities, such as N-acetyl-β-glucosaminidase (EC 126.96.36.199), α1-mannosidase (EC 188.8.131.52) and particularly β-galactosidase (EC 184.108.40.206), are strongly decreased.
3. Degradation of glycosidases by proteases could not explain the decreased glycosidase activity in these faecal extracts.
4. Our data suggest that a modification of the bacterial colonic flora (or of its metabolic activity) occurs in most patients with active Crohn's disease and could be responsible for an impaired colonic salvage of carbohydrates.