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Urethanase in rat tissues.
1Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Japan.
Journal of Toxicology and Environmental Health
|September 1, 1992
Summary
Rat tissues possess urethane-hydrolyzing activity (urethanase), with the highest levels found in kidney lysosomes. This zinc enzyme functions optimally at acidic pH and is inhibited by EDTA.
Area of Science:
- Biochemistry
- Enzymology
- Toxicology
Background:
- Urethane (ethyl carbamate) is a known carcinogen.
- Understanding urethane metabolism is crucial for assessing its toxicological impact.
- Enzymatic hydrolysis of urethane may represent a detoxification pathway.
Purpose of the Study:
- To investigate the presence and characteristics of urethane-hydrolyzing activity (urethanase) in rat tissues.
- To determine the cellular localization and optimal conditions for urethanase activity.
- To elucidate the cofactor requirements of urethanase.
Main Methods:
- Homogenization and subcellular fractionation of rat liver, kidney, and lung tissues.
- Assay of urethanase activity at different pH conditions (acidic vs. neutral).
- Investigation of the effects of Triton X-100, EDTA, and Zn2+ on enzyme activity.
- Determination of intracellular distribution of urethanase in rat kidney.
Main Results:
- Urethanase activity was detected in rat liver, kidney, and lung homogenates.
- Activity was significantly higher under acidic conditions (pH 5.0) compared to neutral conditions (pH 7.0).
- Kidney homogenates exhibited the highest urethanase activity, primarily localized in the lysosomal fraction.
- The enzyme activity was dependent on Zn2+ and strongly inhibited by EDTA, indicating it is a zinc enzyme.
- Optimal pH for urethanase activity was determined to be 5.0.
Conclusions:
- Rat kidney lysosomes contain a significant urethanase activity.
- Urethanase is a zinc-dependent enzyme with optimal activity at acidic pH.
- This enzyme likely plays a role in the detoxification of urethane in rats.