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Nonserine 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, Maryland 20892.
Protein Expression and Purification
|September 1, 1990
Summary
Researchers isolated rat liver esterases resistant to paraoxon. These enzymes hydrolyze various aromatic esters but not amides, revealing broad substrate specificity in liver esterase activity.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Rat liver cytosol contains numerous esterases with diverse functions.
- Serine esterases are a major class, often inhibited by organophosphates like paraoxon.
- Understanding paraoxon-insensitive esterases is crucial for dissecting liver metabolic pathways.
Purpose of the Study:
- To identify and characterize major general esterases in rat liver cytosol.
- To investigate esterases that exhibit resistance to the serine esterase inhibitor paraoxon (diethyl 4-nitrophenyl phosphate).
- To determine the substrate specificity of these isolated enzymes.
Main Methods:
- Isolation of esterases from rat liver cytosol.
- Electrophoretic techniques for assessing enzyme homogeneity.
- Enzyme purification based on hydrolytic activity towards 4-nitrophenyl acetate.
- Substrate specificity assays using various aromatic esters and thiol esters.
Main Results:
- A dozen paraoxon-insensitive esterases were isolated from rat liver cytosol.
- Four of these enzymes were found to be electrophoretically homogeneous.
- All purified enzymes demonstrated broad and overlapping substrate specificity for aromatic esters.
- Thiol esters were confirmed as substrates, while amides were not hydrolyzed.
Conclusions:
- Rat liver cytosol harbors multiple general esterases insensitive to paraoxon.
- These paraoxon-resistant esterases possess broad substrate specificity for aromatic esters.
- The findings contribute to a deeper understanding of esterase diversity and function in mammalian liver.