Aldehyd-Dehydrogenase aus Leber, ein Enzym des Fructosestoffwechsels

Holldorf, August W.; Holldorf, C.; Schneider, Stefan; Holzer, Helmut

doi:10.1515/znb-1959-0405

Cited by 21 publications

(10 citation statements)

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“…By this process the limiting influence of the dissociation of the ADH-NADH complex could be circumvented, as NADH, formed by the dehydrogenation of ethanol to acetate, is reoxidized by glyceraldehyde without prior dissociation from the enzyme. This hypothesis was partly abandoned, when the same workers (36) showed that from an enzyme kinetic point of view it was more probable that glyceraldehyde is dehydrogenated to glycerate, a pathway that is supported by our experiments with fructose alone.…”

Section: Resultsmentioning

confidence: 61%

“…The decrease in the output of lactate and pyruvate suggests that the pathway via glycerate is blocked under these conditions. It has been suggested that acetaldehyde competes efficiently for the aldehyde dehydrogenase responsible for glyceraldehyde oxidation to glycerate (36), as the Km for acetaldehyde is several orders of magnitude smaller than for glyceraldehyde (37).…”

Section: Resultsmentioning

confidence: 99%

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The Mechanism of the Fructose Effect on the Ethanol Metabolism of the Human Liver*

Tygstrup¹,

Winkler²,

Lundquist³

1965

J. Clin. Invest.

141

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Ethanol is normally metabolized at a constant rate by the liver of man and animals. Attempts to change this rate have included treatment with metabolically active substances such as glucose, pyruvate, amino acids, dinitrophenol, insulin, and thyroid hormone. In some cases an increase has been observed, but usually only a very small one. The only exception so far discovered is the effect of fructose, first demonstrated by Stuhlfauth and Neumaier (1). This was confirmed by Pletscher, Bernstein, and Staub (2), who found an average increase in the elimination rate of ethanol of 80% in dogs receiving 1 to 2 g of fructose per kg per hour, and about 70% in human subjects who had fructose infused intravenously in comparable quantities (3). Oral ingestion of fructose in man gave the same result (4). Smaller or no effects have also been reported (5, 6), but in these cases the amount of fructose given was probably -insufficient.Several explanations of the phenomenon (which we shall refer to as the "fructose effect") have been offered, but since none of them were supported by direct experimental evidence, a detailed, quantitative investigation of the problem appeared desirable. Furthermore, it was of interest to study the circulatory and metabolic reactions of the liver during accelerated ethanol metabolism, as previous studies have shown that under normal con-

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Section: Resultsmentioning

confidence: 61%

Section: Resultsmentioning

confidence: 99%

The Mechanism of the Fructose Effect on the Ethanol Metabolism of the Human Liver*

Tygstrup¹,

Winkler²,

Lundquist³

1965

J. Clin. Invest.

141

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“…K , and Vmax of triokinase were obtained as described in the text. The Vmax of aldehyde dehydrogenase a t pH 7.0 was calculated from our result a t pH 9.2 ( Table 1) and the pH activity curve reported by Holldorf et al [9]; the K , is taken also from Holldorf et al [9]. The Vmax of alcohol dehydrogenase was calculated from the activity observed at a glyceraldehyde concentration of about its K , ( potential action of these enzymes in near physiological conditions.…”

Section: T H E Glyceraldehyde Metabolic Crossroadsmentioning

confidence: 90%

Enzymes Involved in Fructose Metabolism in Liver and the Glyceraldehyde Metabolic Crossroads

Sillero

Sols

1969

European Journal of Biochemistry

126

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Fructokinase, the B isoenzyme of fructosediphosphate aldolase and triokinase, the three enzymes of the Hers' pathway for fructose metabolism, are constitutive in adult rats.A quantitative model of the metabolic crossroads of D-glyceraldehyde has been developed. This model permits a prediction of the relative contributions of the phosphorylative, oxidative and reductive pathways in different conditions. The main pathway for D-glyceraldehyde metabolism in liver is phosphorylation by triokinase. Glyceraldehyde is the center of a metabolic crossroads (Fig.1). Claims have been made for its incorporation into the common glycolytic pathway a t three levels: (a), glyceraldehyde-3-phosphate, by means of a triokinase [6] ; (b), 2-phosphoglycerate, through the action in sequence of aldehyde dehydrogenaseL [7-91 and glycerate kinase [lo-121 ; and (c), dihydroxyacetone phosphate through a pathway that involves 3 enzymic steps: an alcohol dehydrogenase [13-151, glycerol kinase [16,17] and glycerolphosphate oxidase [18].Studies on the activity in rat liver in different nutritional conditions of enzymes potentially involved in fructose metabolism are reported in this paper. A kinetic evaluation of these enzymes, particularly those a t the glyceraldehyde crossroads permits the

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“…Triokinase, described by Hers (2,11) and studied in more detail by our group (15), effects phosphorylation of D-glyceraldehyde to D-glyceraldehyde 3-phosphate by ATP. Aldehyde dehydrogenase (NAD) described by Racker (16), oxidizes D-glyceraldehyde to D-glyceric acid (17,18), which is then phosphorylated by ATP and D-glycerate kinase of liver to 2-phospho-Dglyceric acid (19,20) Holzer and Schneider (27,28) with alcohol dehydrogenase from bovine liver, the reduction of glyceraldehyde will be discussed together with the oxidation of ethanol on the surface of the enzyme. In this paper, activities of enzymes involved in fructose metabolism in the human liver will be described and compared with enzyme levels found in rat liver (1).…”

Section: Introductionmentioning

confidence: 99%

Enzymes of fructose metabolism in human liver

Heinz¹,

Lamprecht²,

Kirsch³

1968

J. Clin. Invest.

129

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A B S T R A C T The enzyme activities involved in fructose metabolism were measured in samples of human liver. On the basis of U/g of wet-weight the following results were found: ketohexokinase, glycerol kinase, 0.62. Sorbitol dehydrogenases (25.0 U/g), hexosediphosphatase (4.06 U/g), hexokinase (0.23 U/g), and glucokinase (0.08 U/g) were also measured. Comparing these results with those of the rat liver it becomes clear that the activities of alcohol dehydrogenases (NAD and NADP) in rat liver are higher than those in human liver, and that the values of ketohexokinase, sorbitol dehydrogenases, and hexosediphosphatase in human liver are lower than those values found in rat liver. Human liver contains only traces of glycerate kinase.The rate of fructose uptake from the blood, as described by other investigators, can be based on the activity of ketohexokinase reported in the present paper. In human liver, ketohexokinase is present in a four-fold activity of glucokinase and Requests for reprints should be addressed to Dr.

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Aldehyd-Dehydrogenase aus Leber, ein Enzym des Fructosestoffwechsels

Cited by 21 publications

References 0 publications

The Mechanism of the Fructose Effect on the Ethanol Metabolism of the Human Liver*

The Mechanism of the Fructose Effect on the Ethanol Metabolism of the Human Liver*

Enzymes Involved in Fructose Metabolism in Liver and the Glyceraldehyde Metabolic Crossroads

Enzymes of fructose metabolism in human liver

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