Characterization of β-Glucosidase and β-Glucuronidase of Alkalotolerant Intestinal Bacteria

Abstract

The number of alkalotolerant intestinal bacteria was 1% of the total flora in humans and 0.8% of those in rats. The β-glucosidase and β-glucuronidase activity of these intestinal bacteria was induced by elevating the pH of the medium, but the growth was not changed. The enzyme activity in a medium of pH 7 was 5- to 10-fold higher than that in a medium of pH 6. Isolated bacteria from human and rat feces were cultured in a pH 5 general anaerobic medium (GAM) broth to reach a stationary phase, then the pH of the media was changed from 5 to 8. Both β-glucosidase and β-glucuronidase were increased 9.2—12.1-fold. The activity of these enzymes was also increased 2—16-fold by adding substrates (p-nitrophenyl-β-D-glucuropyranoside or p-nitrophenyl-β-D-glucuronide). β-Gluc-uronidase(s) was inhibited by saccharic acid 1, 4-lactone or D-glucuronic acid. However, when lactulose was added to the medium, and then intestinal microflora were inoculated in the medium, the productivity of these enzymes dra-matically decreased. We thus contend that the induction of the β-glucosidase and β-glucuronidase of intestinal bacteria by a high pH can cause colorectal cancer. © 1994, The Pharmaceutical Society of Japan. All rights reserved.