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Rat liver alcohol dehydrogenase. I. Purification and characterization
Analytical Biochemistry
|September 1, 1983
Summary
Researchers purified alcohol dehydrogenase from rat livers, achieving over 240-fold purity. Kinetic studies determined key constants for ethanol oxidation, aiding in understanding in vivo metabolic rates.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Alcohol dehydrogenase (ADH) plays a crucial role in ethanol metabolism.
- Understanding ADH kinetics is vital for comprehending alcohol's physiological effects.
Purpose of the Study:
- To purify and characterize alcohol dehydrogenase from male Fischer-344 rat livers.
- To determine the kinetic parameters of purified ADH for ethanol oxidation.
Main Methods:
- Enzyme purification using differential centrifugation, ammonium sulfate precipitation, and multiple chromatography steps (DEAE-Affi-Gel Blue, Affi-Gel Blue, AMP-agarose, HPLC).
- Enzyme characterization via SDS-PAGE, analytical isoelectric focusing, and kinetic assays.
- Determination of kinetic constants (Vmax, Km, dissociation constant) at 37°C and pH 7.4.
Main Results:
- Achieved >240-fold purification of ADH, yielding a single protein band (Mr ~40,000) on SDS-PAGE.
- Identified two protein and two activity bands between pH 8.8-8.9 via isoelectric focusing.
- Determined kinetic constants: Km for ethanol (0.156 mM), Km for NAD+ (0.176 mM), and dissociation constant for NAD+ (0.306 mM).
- Calculated in vivo ethanol oxidation rate at 2.4 µM/min/g liver at pH 7.4 and 10 mM ethanol.
Conclusions:
- The study successfully purified and characterized rat liver alcohol dehydrogenase.
- Kinetic data provides insights into the enzyme's function in ethanol metabolism.
- Extrapolated in vivo rates offer a quantitative measure of hepatic ethanol oxidation.