STABILITY AND ENZYMATIC HYDROLYSIS OF ALIPHATIC TYPE N+-GLUCURONIDE METABOLITES
| dc.contributor.advisor | Hawes, E.M. | |
| dc.creator | Kowalczyk, Iwona | |
| dc.date.accessioned | 2023-12-13T16:42:39Z | |
| dc.date.available | 2023-12-13T16:42:39Z | |
| dc.date.issued | 1994 | |
| dc.date.submitted | 1994 | |
| dc.description.abstract | Quaternary ammonium-linked glucuronide metabolites (N*-glucuronides) are known for at least 20 drugs with an aliphatic tertiary amine group. Nevertheless research into these metabolites, including their toxicity is lacking. There is even lack of information about their stability under conditions that might be encountered physiologically or in their assays. The major objectives of the present work were to examine N+-glucuronide metabolites with respect to their stability over the pH range 1-11 and the effect of J3-glucuronidase treatment from various sources. Structurally diverse N4--glucuronide metabolites were included in the study, namely metabolites where N+-glucuronidation had occurred at either an acyclic (chlorpromazine N+-glucuronide and doxepin N+-glucuronide) or a cyclic aliphatic tertiary amine group (clozapine N+-glucuronide and cyclizine N+-glucuronide). Aqueous solutions of three N+-glucuronide metabolites were stored at room temperature (18-22°C) over the pH range 1-11 for a 3-4 month period. No rapid hydrolysis occurred. All three substrates were stable over the pH range 4-10 for at least three months. Clozapine N+-glucuronide and cyclizine N+-glucuronide were unstable over the pH range 1-3 while cyclizine N+-glucuronide and doxepin N+-glucuronide were unstable at pH 11. ß-Glucuronidase from three types of sources is commonly employed in in vitro studies: bacteria, bovine liver and mollusks. One preparation from each of these sources (about two units of enzyme per µg of substrate) was incubated with all four N+-glucuronide metabolites and phenolphthalein 0-glucuronide in pH 5.0 and pH 7.4 buffers at 37°C for 48 h. Phenolphthalein O-glucuronide was extensively hydrolyzed by each of the enzyme preparations. In contrast, three of the N+-glucuronide metabolites were not affected by g-glucuronidase preparations from bovine liver and Helix pomatia. Only clozapine N+-glucuronide was readily hydrolyzed by all three 1-glucuronidase preparations examined. E. coli was the only enzyme source which resulted in hydrolysis of all four N+-glucuronide metabolites and in subsequent studies, the optimal pH was found to be in the range of 6.5-8. Each previous study of the effect of g-glucuronidase on aliphatic type N+-glucuronide metabolites has been limited to one substrate and one enzyme source. The common usage of g- glucuronidases from bovine liver and Helix pomatia in these previous studies is surprising in view of the observed resistance of the N+-glucuronides to these two enzyme sources in the present work. | |
| dc.identifier.uri | https://hdl.handle.net/10388/15344 | |
| dc.title | STABILITY AND ENZYMATIC HYDROLYSIS OF ALIPHATIC TYPE N+-GLUCURONIDE METABOLITES | |
| dc.type.genre | Thesis | |
| thesis.degree.department | Toxicology | |
| thesis.degree.grantor | University of Saskatchewan | en_US |
| thesis.degree.level | Masters | |
| thesis.degree.name | Master of Science (M.Sc.) |