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EMBDEN (1) demonstrated that glucose was metabolized to lactate in an isolated perfused liver by the glycolytic pathway. With the development of more sophisticated techniques than those employed by EMBDEN and other earlier workers, it is now possible to study quantitatively the extent and nature of glycolysis in liver.

Dans le but d'expliquer l'hypoglycemie croissante observee durant la cancerisation du tissu hepatique par le DAB, nous avons mesure les activites des enzymesocles de la voie Embden-Meyerhof: glucokinase, phosphofructokinase et pyruvate-kinase. Toutes ces activites diminuent en valeur absolue. En comparant les activites de la glucokinase et de la phosphofructokinase avec celles de la glucose-6-phosphatase et de la fructose-1,6-diphosphatase, on s'apercoit que la degradation des glucides prend une importance croissante sur leur formation, au cours de la cancerisation. En outre, une fraction accrue des glucides emprunte la voie des pentose phosphates. On discute la signification de ce fait. MODIFICATIONS OF CARBOHYDRATE METABOLISM OBSERVED DURING HEPATOCARCINOGENESIS BY DAB1 . II. MODIFICATION OF THE RELATIVE ROLE OF THE EMBDEN-MEYERHOF PATHWAY In an attempt to find an explanation for the increasing hypoglycaemia observed during DAB-induced cancer invasion of hepatic tissue, we measured the activities of key enzymes of the Embden-Meyerhof pathway—i.e. glucokinase, phosphofructokinase, and pyruvate kinase. All these activities diminished in absolute terms. A comparison of glucokinase and phosphofructokinase activities, on the one hand, with those of glucose-6-phosphatase and fructose-1,6-diphosphatase, on the other, revealed that glucide breakdown progressively outstrips glucide formation during cancer invasion. Furthermore, a larger proportion of the glucides makes use of the pentose phosphate pathway. The significance of this finding is discussed.

The acid soluble phosphorus fraction of cells of Pseudomonas aeruginosa harvested from a glucose medium was found to consist mainly of difficultly hydrolyzable compounds. None of the fractions contained reducing compounds even after 12 hr. hydrolysis with normal hydrochloric acid nor could fructose be detected. It could therefore be concluded that glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, and hexose diphosphate were absent. Analysis of a glucose solution that had been metabolized by cells of this organism under conditions of fluoride inhibition confirmed the analysis of the cellular material. The lack of normal intermediates of the Embden–Meyerhof scheme is discussed in relation to the gluconic acid, 2-ketogluconic acid pathway of glucose oxidation.

The amount of lactate and pyruvate production by kidney cortex homogenates (cell sap and microsomal fraction) from all intermediates of the glycolytic pathway has been investigated in normal and 3,3′,5-triiodo-l-thyronine-treated rats. In normal animals the lactate and pyruvate production increases steadily from glucose (154 nmoles × mg protein−1× h−1) through phosphoenolpyruvate (31.850 nmoles × mg protein−1 h−1). The addition in vitro of triiodo-l-thyronine to kidney cortex homogenates has no significant effect on lactate production. In the animals treated for 5 days with 1 mg/kg body weight and per diem of triiodo-l-thyronine, the lactate and pyruvate formation from various intermediates of the Embden-Meyerhof pathway is significantly (P < 0.01) increased: from glucose 225% of the control value, from glucose 6-phosphate and fructose 6-phosphate, 192%, from fructose 1,6-bisphosphate and glyceraldehyde 3-phosphate, 132%, and from 3-phosphoglycerate and 2-phosphoglycerate, 120%. No significant increase in lactate and pyruvate production has been observed using either phosphoenolpyruvate or pyruvate as substrates.

Evidence demonstrating the occurrence of some of the glycolytic enzymes in the two-spotted spider mite, Tetranychus telarius L., has been obtained. The glycolytic pathway in mites appears to be similar to the Embden–Meyerhof type described for other organisms.The enzymes shown to be present in the mite are: phosphohexoisomerase, phosphofructokinase, aldolase, α-glycerophosphate dehydrogenase, and glyceraldehyde-3-phosphate dehydrogenase. The hexokinase and lactic dehydrogenase, if present, are in very low titre. The end products of glycolysis in the mites were shown to be α-glycerophosphate and pyruvate.

The enzymic flux rates through the Embden-Meyerhof pathway and the nucleotides of the liver have been measured in vivo with the [32P]Pi-tracer technique. The specific radioactivities of 15 positions in 11 metabolites have been measured within the first minute after injection of carrier-free [32P]Pi. The results have been treated with the analogue computer technique. The main conclusions are: 1 The turnover of all liver compounds examined is in the range of from seconds to minutes. The velocity of oxidative phosphorylation is so high that within 30 sec after the tracer injection prestationary kinetics is observed, indicating that the turnover of the γ-P position of ATP amounts to more than 25 μmoles per g fresh liver per min. 2 The labelling of ATP-γ-P is rapidly redistributed within the other nucleotide β- and γ-P-positions, the reactions of the nucleoside diphosphokinase type being more rapid than with the monophosphokinase type. 3 The rate of net glycolysis or gluconeogenesis is less than 0.1 μmoles per g per min in the postabsorptive state. Synthesis of glycogen or UDP-glucuronic acid via UDPG is less than 0.3 μmoles per g per min. The absolute turnover rate of glucose 6-phosphate is about 3 μmoles per g per min. The pathway of glucose 6-phosphate formation and the fate of glucose 6-phosphate cannot be measured on the basis of 32P-experiments alone. 4 Phosphofructokinase as well as aldolase and fructose 1,6-biphosphate phosphohydrolase are inhibited in vivo. In the latter two cases, adequate kinetic explanation of this phenomenon is not available from in vitro results of the literature. The isotope flux via glucosephosphate isomerase amounts to 0.4 μmoles per g per min. This is about one order of magnitude smaller than expected from the maximal activity and from the kinetic behaviour of the enzyme in vitro. 5 Synthesis of about 0.7 μmoles of glycerol 3-phosphate from ATP and glycerol takes place per g per min. At least 0.7 μmoles of phosphoenolpyruvate are synthesized per g per min without being converted to fructose 1,6-biphosphate. The fate of phosphoenolpyruvate is unknown. Reconversion to pyruvate or conversion to lipid glycerol is possible.

The specific activities of certain enzymes of the Embden-Meyerhof-Parnas (EMP) and pentose phosphate (PP) pathways varied in cultures of Aspergillus niger in relation to the stage of the growth cycle and the nature of the growth medium. At 24 h from spore inoculation the levels of PP pathway enzymes glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and transketolase were higher in extracts from non-sporulating than from sporulating mycelium. Correspondingly, the levels of most EMP pathway enzymes were higher in extracts from sporulating than from non-sporulating mycelium. These fluctuations in enzyme levels occurred well in advance of any morphological evidence of sporulation. At later stages of growth (48–96 h) the levels of the enzymes were similar in extracts from both types of mycelium. Radiorespirometric patterns for the oxidation of specifically labelled [14C] glucose implied that the EMP and PP pathways were active in both types of mycelium. The contribution of the PP pathway was highest in young non-sporulating mycelium whereas the contribution of the EMP pathway was highest in sporulating mycelium of corresponding age.

The paper describes the detection of enzymes of the Embden-Meyerhof and pentose phosphate pathways by spectrophotometry and fluorimetric assays of cell-free extracts of the Basidiomycete Polyporus brumalis.

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An verschiedenen Muskeltypen einschlieslich des Myometriums wurden die Aktivitaten von Enzymen des energieliefernden Stoffwechsels bestimmt und die Ergebnisse in Form von Aktivitatsmustern wiedergegeben.