Effect of Secreted Bacteroides Proteases on Human Intestinal Brush Border Hydrolases

Abstract

A B S T R A C T Selected bacteroides species secreted various amounts of protease and glycosidase into their growth medium. Bacteroides vulgatus, distasonis, and ovatus secreted the most (31-60% of total). The secreted protease was similar in action to the protease within the organism, in that it had a broad pH optimum of 6-9, a Km app. for casein of 0.1 ,uM, and was inhibited by benzamidine, phenylmethylsulfonyl fluoride, diisopropylfluorophosphate (DIFP), and by an elastase inhibitor, Ac(Ala)3AlaCH2Cl.Exposure of human brush border preparations to the secreted protease reduced maltase and sucrase activities; the reduction could be prevented by DIFP. In contrast, brush border alkaline phosphatase activity either did not change or increased after exposure to bacterial secretions. >90% inhibition of secreted glycosidase using EDTA and p-chloromercuribenzoic acid did not prevent the reduction of brush border maltase and sucrase activity, suggesting that glucosidases were not likely to be involved in the destruction of brush border enzymes. Moreover, the bacterial proteases caused only a small net release of active maltase or sucrase from the brush border. Most of the loss of activity was due to destruction of the enzyme. Proximal bowel fluid of three patients with overgrowth contained DIFP-inhibitable protease that destroyed sucrase in isolated brush borders. A Bacteroides species was isolated from each sample that secreted protease and destroyed brush border sucrase. We conclude that in bacterial overgrowth syndromes, brush border damage may occur from protease(s) secreted by Bacteroides.

Small bowel bacterial overgrowth: A negative factor in gut adaptation in pediatric SBS

“…Both anaerobes and aerobes have been identified as responsible for the damage to the intestinal mucosa in SBS. Facultative anaerobes adhere to the epithelium and produce endotoxins, whereas aerobes produce enzymes (proteases) and other products that result in mucosal injury [16,34].…”

Role of lysophosphatidylcholine in brush-border intestinal alkaline phosphatase release and restoration

“…These findings suggest that duodenal and jejunal BBM-IAP released into the lumen during fat digestion might act within the lumen of the ileum and large intestine to detoxify LPS. IAP is relatively resistant to pancreatic proteases, consistent with the possibility that some IAP might survive transit to the colonic lumen in an active form (23).…”

The NADH-dependent glutamate dehydrogenase enzyme of Bacteroides fragilis Bf1 is induced by peptides in the growth medium

“…B. fragilis has been shown to produce several proteases (Gibson & Macfarlane, 1988a, b) and some protease enzymes from this organism have been cloned and characterized (Van Tassel et al, 1992;Chen et al, 1995;Kling et al, 1997;Franco et al, 1997). It has been suggested that proteases play a role in the pathogenesis of this organism (Riepe et al, 1980;Moncrief et al, 1995) and it has also been demonstrated that the levels of protease production vary with the availability of ammonia (MacFarlane et al, 1993), with less protease activity being evident under excess ammonia conditions. The regulation of gdhB by organic nitrogen may be linked to protease activity and the breakdown of proteins in vivo, and hence to pathogenesis.…”