E. coli beta-glucuronidase is associated with severe side effects caused by the chemotherapy pro-drug CPT-11. CPT-11 is converted to the toxic active metabolite SN-38, which is a topoisomerase I inhibitor. In the liver, SN-38 is glucuronidated to SN-38G. SN-38G then enters the gastrointestinal tract, where bacterial beta-glucuronidase cleaves the glucuronide group from SN-38G, causing intestinal damage. The commercial inhibitor Z-77 blocks the interaction of beta-glucuronidase and SN-38G and has been shown to decrease the damage associated with CPT-11. E. coli beta-glucuronidase contains a functional loop not found in the human form of the enzyme. This so-called bacterial loop controls species selectivity of the Z-77 inhibitor. A phenylalanine (F365) in the bacterial loop is thought to be essential to the binding of Z-77. To determine the importance of this phenylalanine, the residue was systematically mutated to tyrosine, tryptophan, alanine, and leucine. The effect of these mutations of Z-77 binding were characterized by a standard phenolphthalein glucuronide enzymatic assay. This project will provide a better understanding of the binding of the Z-77 inhibitor and may aid in improving Z-77 and other inhibitors alike.

Role of F365 in inhibitor binding by Escherichia coli beta-glucuronidase

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.