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Characterization of human erythrocyte aldehyde dehydrogenase
J W Rawles1, D L Rhodes, J J Potter
1Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
Biochemical Pharmacology
|November 1, 1987
Summary
Human erythrocyte aldehyde dehydrogenase, similar to liver cytosolic aldehyde dehydrogenase, was purified. This enzyme may protect tissues from acetaldehyde toxicity during ethanol metabolism.
Area of Science:
- Biochemistry
- Enzymology
- Human Physiology
Background:
- Aldehyde dehydrogenase (ALDH) is crucial for metabolizing toxic aldehydes.
- The role of erythrocyte ALDH in ethanol metabolism and extrahepatic tissue protection is not fully understood.
Purpose of the Study:
- To purify and characterize human erythrocyte aldehyde dehydrogenase.
- To compare its properties with human liver cytosolic aldehyde dehydrogenase.
- To investigate the effect of magnesium on enzyme activity.
Main Methods:
- Purification of human erythrocyte ALDH to homogeneity.
- Enzyme characterization using starch gel electrophoresis and isoelectric focusing.
- Kinetic analysis and determination of kinetic parameters (e.g., Michaelis-Menten constant).
- Assays to determine the effect of magnesium ions on enzyme activity.
Main Results:
- Purified erythrocyte ALDH is a tetramer with a molecular weight of 230,000 daltons and an isoelectric point of 5.0.
- Enzyme properties (pH optimum, Km for acetaldehyde, inhibition by disulfiram) resemble human liver cytosolic ALDH.
- Low magnesium concentrations enhanced activity, while higher concentrations caused uncompetitive inhibition by increasing NADH binding.
Conclusions:
- Human erythrocyte ALDH shares biochemical and kinetic properties with its liver counterpart.
- Erythrocyte ALDH may play a role in metabolizing acetaldehyde that escapes the liver.
- This enzyme could protect extrahepatic tissues from acetaldehyde toxicity during ethanol metabolism.