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Aspirin hydrolyzing esterases from rat liver cytosol
D H Kim1, Y S Yang, W B Jakoby
1Laboratory of Biochemistry and Metabolism, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Biochemical Pharmacology
|August 1, 1990
Summary
Two soluble serine esterase isozymes in rat liver cytosol hydrolyze acetylsalicylic acid. These enzymes have a broad substrate range, indicating a role in detoxification processes.
Area of Science:
- Biochemistry
- Pharmacology
- Enzymology
Background:
- Most esterases are microsomal, but acetylsalicylic acid-hydrolyzing enzymes are cytosolic.
- Understanding aspirin metabolism is crucial for pharmacology and toxicology.
Purpose of the Study:
- To purify and characterize the enzymes responsible for acetylsalicylic acid hydrolysis in rat liver cytosol.
- To investigate the properties and substrate specificity of these enzymes.
Main Methods:
- Purification of two soluble isozymes from rat liver cytosol to homogeneity.
- Characterization of the purified enzymes, including molecular weight determination and substrate specificity analysis.
- Comparison with other cytoplasmic enzymes active with aspirin.
Main Results:
- Two homogeneous serine esterase isozymes (Mr 35,000) were isolated from rat liver cytosol.
- Both isozymes exhibited a wide substrate spectrum, typical of detoxifying enzymes.
- A very low Km for acetylsalicylic acid was observed for both purified isozymes.
- Three other high molecular weight (approx. 220,000) cytoplasmic enzymes active with aspirin were identified.
Conclusions:
- Rat liver cytosol contains distinct serine esterases responsible for acetylsalicylic acid hydrolysis.
- These enzymes play a significant role in aspirin detoxification due to their broad substrate specificity and high affinity.
- The presence of multiple cytoplasmic enzymes suggests complex aspirin metabolism pathways.