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Purification and characterization of a novel 46.5-kilodalton esterase from mouse hepatic microsomes
K Watanabe1, Y Kayano, T Matsunaga
1Department of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Hokuriku University, Kanazawa, Japan.
Abstract:
A novel membrane-bound esterase was purified from mouse hepatic microsomes. The purified protein (ES46.5K) showed a single protein-staining band on sodium dodecyl sulfate-polyacrylamide gel with a minimum molecular weight of 46.5 Kdalton. ES46.5K possessed esterase activity toward 11-acetoxy-delta 8-tetrahydrocannabinol (11-OAc-delta 8-THC) (27.1 mumol/min/mg protein) and p-nitrophenylacetate (119 mumol/min/mg protein), and these activities were 38 and 47 times, respectively, as high as those of microsomes. The N-terminal amino acid sequence of the protein was as follows: G-K-T-I-S-L-L-I-S-V-V-L-V-A-Y-Y-L-Y-I. This sequence has no homology to those of the known carboxylesterases, indicating that this enzyme is a novel type of esterase bound to the microsomal membrane.
Insights
Researchers identified a novel mouse hepatic microsomal esterase, ES46.5K. This enzyme exhibits significant esterase activity and possesses a unique N-terminal sequence, suggesting it represents a new class of membrane-bound esterases.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Microsomal fractions are crucial for cellular metabolism.
- Esterases play vital roles in detoxification and drug metabolism.
- Understanding novel enzymes aids in elucidating complex biological pathways.
Purpose of the Study:
- To purify and characterize a novel esterase from mouse hepatic microsomes.
- To determine the enzymatic activity and substrate specificity of the purified esterase.
- To analyze the protein's N-terminal amino acid sequence for homology to known enzymes.
Main Methods:
- Purification of membrane-bound esterase from mouse hepatic microsomes.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for molecular weight determination.
- Enzyme activity assays using 11-acetoxy-delta 8-tetrahydrocannabinol and p-nitrophenylacetate as substrates.
- N-terminal amino acid sequencing.
Main Results:
- A novel membrane-bound esterase, designated ES46.5K, was successfully purified.
- ES46.5K exhibited high specific activity towards 11-acetoxy-delta 8-tetrahydrocannabinol and p-nitrophenylacetate.
- The enzyme's molecular weight was determined to be 46.5 kDa.
- N-terminal sequencing revealed no homology to known carboxylesterases.
Conclusions:
- ES46.5K represents a novel type of membrane-bound esterase.
- This enzyme may play a significant role in hepatic microsomal functions.
- Further research is warranted to elucidate its physiological and pharmacological relevance.