Showing papers on "Aldehyde dehydrogenase published in 1972"

Intracellular localization of aldehyde dehydrogenase in rat liver

Abstract: 1. Distribution of aldehyde dehydrogenase activity in rat liver was studied by measuring the rate of disappearance of acetaldehyde in the presence of each of the subcellular fractions. These were obtained by rough separation of particulate fractions from the soluble portion of the cell, by differential centrifugation, and by isopycnic gradient centrifugation. 2. The maximal rate of acetaldehyde oxidation was 3.7 mumol/min per g, with an apparent K(m) value below 10(-5)m. The highest rate of activity was observed in phosphate buffers of high P(i) concentration (above 60mm). 3. The activity measured was completely dependent on NAD(+). 4. The microsomal fraction and the nuclei were inactive in the assay. Of the total activity 80% was found in the mitochondrial fraction and the remaining 20% in the cytoplasm. 5. The distribution pattern is important from the point of view of acetaldehyde oxidation during ethanol metabolism. The apparent discrepancy of the results obtained by different workers and the localization of acetaldehyde oxidation in vivo is discussed.

Enzymes catalysing ethanol metabolism in neural and somatic tissues of the rat

Abstract: — The enzymes catalysing ethanol metabolism, alcohol dehydrogenase (EC 1.l.1.1) and aldehyde dehydrogenase (EC 1.2.1.3), were assayed in a variety of neural and somatic tissues of the rat, the human counterparts of which are known to be vulnerable to excessive ethanol. The activity of alcohol dehydrogenase was assayed by the coupled oxidation of ethanol and reduction of lactaldehyde, a method which we have recently found to be sufficiently sensitive and specific to measure the relatively low levels of activity in whole brain. Detectable activities of these enzymes were found in peripheral nerve, skeletal muscle, retina, optic nerve and various regions of brain, as well as in a variety of non-neural tissues. The levels of the enzymic activities in all tissues were markedly lower than those of liver, but probably sufficient to perform a local function in the metabolism of ethanol or other endogenous substrates. The activity of alcohol dehydrogenase in the various tissues, like that of liver, was confined to the cytosol and exhibited kinetic properties and responses to inhibitors almost identical to those of the liver enzyme. We consider the results to be consistent with the hypothesis that the pathological effects of alcohol may be related, at least in part, to local mechanisms for the metabolism of alcohol.

On the Role of Alcohol Dehydrogenase in ω‐Oxidation of Fatty Acids

Abstract: Rat and horse liver alcohol dehydrogenase was found to oxidize ω2-hydroxyfatty acids into the corresponding oxofatty acids but showed no significant activity towards ω1-hydroxyfatty acids. However, ω1-hydroxyfatty acids were oxidized into the corresponding dicarboxylic acids by a combination of horse or rat liver alcohol dehydrogenase with rat liver aldehyde dehydrogenase. The ratio between ω-hydroxyfatty acid dehydrogenase activity and ethanol dehydrogenase activity increased about two-fold through the steps used in the preparation of alcohol dehydrogenase from rat liver. Oxidation of 17-dl-hydroxystearic acid by rat liver alcohol dehydrogenase was inhibited by pyrazol, ethanol and 3β-Lhydroxy-5β-cholanoic acid. Oxidation of ethanol and 3β-hydroxy-5β-cholanoic acid by rat liver alcohol dehydrogenase was inhibited by ω-hydroxy-fatty acids. Long-chain ω1- and ω2-hydroxyfatty acids were oxidized by rat liver alcohol dehydrogenase much more efficiently than medium-chain ω1- and ω2-hydroxyfatty acids and the Km, values for oxidation of the long-chain ω-hydroxyfatty acids were 10–40 μM. The rate of oxidation of 17-l-hydroxystearic acid by rat and horse liver alcohol dehydrogenase was faster than that of oxidation of 17-d-hydroxystearic acid. Experiments with different monohydroxylated stearic acids as substrates for rat liver alcohol dehydrogenase showed that significant activity appeared when the distance between the hydroxyl group and the carboxyl group was more than 12 carbon units. The activity increased with increasing distance between the hydroxyl group and the carboxyl group. Lauryl alcohol but not stearyl alcohol was oxidized by rat liver alcohol dehydrogenase to a significant extent.

Aldehyde Dehydrogenases in Rat Liver

Abstract: Two enzymes (I and II) with NAD+-dependent aldehyde dehydrogenase activity have been separated and partially purified from the supernatant fraction of rat liver. Resolution was effected by DEAE-cellulose column chromatography. In addition to the differences in charge properties, these two proteins differ in substrate specificity, that of enzyme II being comparatively restricted. Enzyme I has a relatively sharp optimum in activity at pH 8 whereas enzyme II exhibits an optimal range between pH 8 and 9.5. Both enzymes are strongly inhibited by low concentrations of p-chloromercuribenzene sulfonic acid and this inhibition can be reversed by dithiothreitol. Both enzymes are also inhibited by arsenite; inhibition of enzyme I is enhanced by mercaptoethanol but inhibition of enzyme II is not so affected. Molecular weight estimation by gel filtration indicates each protein has a molecular weight of approximately 180 000.

The Purification and Properties of an NADPH‐Linked Aldehyde Reductase from Pig Brain

Abstract: 1 An NADPH-linked aldehyde reductase has been purified some 600-fold from the supernatant fraction of a pig brain homogenate. 2 Subcellular distribution studies show that the enzyme is almost exclusively located in the cytosol. 3 The enzyme has a molecular weight of 29000 and an isoelectric point of 5.8. 4 The enzyme reduces a wide range of aliphatic and aromatic aldehydes, including some biogenic aldehydes. Ketones are not reduced. 5 Specificity studies carried out on the enzyme suggest that substituted phenylglycolaldehydes are reduced far more readily than the corresponding substituted phenylacetaldehydes. 6 Ethanol, reserpine and several aldehyde dehydrogenase and liver alcohol dehydrogenase inhibitors do not affect the activity of brain NADPH-linked aldehyde reductase. 0.1 mM sodium barbitone markedly inhibits the enzyme.

Ethanol-induced adaptation of alcohol dehydrogenase activity in rat brain.

Abstract: ALTHOUGH the presence of alcohol dehydrogenase (ADH) in cerebral tissue has been established1, a physiological role for such a brain ethanol-oxidizing system has been unclear. The brain may be more biochemically adaptive than was once thought2; thus, it seemed possible that brain ADH may be substrate-induced. We now report that significant elevations of brain ADH activity occur in alcohol-imbibing rats; no changes from control values were found in liver ADH, liver aldehyde dehydrogenase (AldDH), or brain AldDH activities.

Aldehyde Derivatives of Indoleamines and the Enhancement of their Binding onto Brain Macromolecules by Pentobarbital and Acetaldehyde

Abstract: ALDEHYDE derivatives of catecholamines and of indoleamines, for example, of serotonin, are formed in the brain by the action of monoamine oxidase (MAO)1,2. Further metabolic transformation proceeds via an NAD-dependent aldehyde dehydrogenase (ADH)3,4 and an NADPH-dependent aldehyde reductase (ADR)5, which has been shown to be inhibited by low concentrations of barbiturates, both in vitro6,7 and in vivo8. Aldehyde dehydrogenase, on the other hand, has a wide substrate specificity and a given substrate may compete for oxidation with others (such as competition between acetaldehyde and 5-hydroxyindoleacetaldehyde9). These metabolic relationships would be expected, in proper circumstances (that is, in the presence of barbiturates or acetaldehyde), to increase the steady state concentration of aldehyde intermediates of biogenic amines.

Genetic basis of phenobarbital-induced increase in aldehyde dehydrogenase: implications for alcohol research.

Abstract: While the genetic basis for alcohol preference in human beings is a subject of much debate, this is not the case in animals. The studies by McCleam and Rodgersl and Mardones and colleagues2 have clearly demonstrated that selected strains of animals prefer alcohol to water as their drinking fluid. The biochemical basis for this effect has not yet been determined, although studies have demonstrated differences in liver alcohol and aldehyde dehydrogenase enzymes between these strains of animak3*4 Other studies in progress in our laboratory are closely examining changes in brain neurotransmitters as a possible basis for differences in drinking behavior. Of course, the metabolism of ethanol and acetaldehyde is closely linked to the metabolism of these neurotransmitter^.^ Our approach to this problem has also been from another point of view. We have concentrated on the control of the synthesis and degradation of those enzymes responsible for alcohol, aldehyde, and amine metabolism. In the course of these studies it was found that the stimulation of aldehyde dehydrogenase activity in the liver by phenobarbitala was present only in genetically selected strains of rats. Studies by Redmond and Cohen' in mice have shown an increase in liver aldehyde dehydrogenase. While the initial observations have been serendipitous, it will eventually allow us to determine what these changes in aldehyde dehydrogenase activity make in drinking behavior, addiction to alcohol, and-cross tolerance to other CNS depressant drugs.