Glycolysis

About: Glycolysis is a research topic. Over the lifetime, 10593 publications have been published within this topic receiving 507460 citations. The topic is also known as: GO:0006096 & glycolysis.

Glycolysis in Trypanosoma brucei

Abstract: The possibility that the glycosomes present in the bloodstream form of Trypanosoma brucei [Opperdoes, F. R. and Borst, P. (1977) FEBS Lett. 80, 360--364] constitute a separate pool of glycolytic intermediates within the cell was investigated. In titrations of intact cells with digitonin, a differential activation of glycolytic enzymes was observed. Enolase, pyruvate kinase and the cell-sap marker alanine aminotransferase were activated at 0.05 mg digitonin per mg protein. The nine glycosomal enzymes involved in the conversion of glucose and glycerol into 3-phosphoglycerate were activated only at digitonin concentrations between 0.7 and 9.8 mg/mg protein. In subcellular fractions the activities of the latter enzymes were all latent between 70 and 92%. Latency was abolished by addition of 0.1% Triton X-100 or partly by five cycles of freezing and thawing. We conclude that the glycosomal enzymes are surrounded by a membrane, which forms a permeability barrier to intermediates and co-factors of glycolysis. The concentrations of glycolytic intermediates and of adenine nucleotides were measured under aerobic conditions as well as in the presence of 1 mM salicylhydroxamic acid, a respiratory inhibitor. Addition of salicylhydroxamic acid caused the following changes: (a) The levels of almost all glycolytic intermediates measured decreased. Glycerol-3-phosphate, however, increased fourfold. (b) The phosphate potential was drastically lowered from 2900 to 450 M-1. (c) The trypanosomes became more reduced, as monitored by a change in the apparent redox state of the NADH/NAD+ courple from E'h = -189 to E'h = -219 mV. From the high levels of metabolite concentrations found and from comparison of the apparent mass-action ratios calculated for the separate glycolytic reactions with those for other organisms, we conclude that in bloodstream form T. brucei the glycolytic intermediates are present in the glycosomes as well as in the cytosol and that the two pools of intermediates equilibrate with each other, despite the presence of the glycosomal membrane.

Glycolysis as Primary Energy Source in Tumor Cell Chemotaxis

Abstract: The energy requirements via glycolytic pathways were directly measured in migrating tumor cells. Motility in the metastatic human melanoma cell line A2058, stimulated by insulinlike growth factor I (IGF-I), depends on glycolysis in the presence of glucose as its principal source of energy. Motility in glucose-free medium was 75% reduced and utilized mitochondrial respiration (inhibited by oligomycin). With increasing (physiologic) glucose concentrations, there was a dramatic shift to anaerobic glycolysis as the energy source and 93% elimination of the oligomycin inhibition of motility. Oxamate, an inhibitor of glycolysis, inhibited motility at all glucose concentrations. CO2 production from glycolysis and from the hexose monophosphate shunt was measured in migrating tumor cells. The time course and glucose-dose dependence of glycolytic CO2 production correlated directly with motility. In contrast, mitochondrial CO2 production was inversely related to glucose concentration. A monoclonal antibody for the IGF-I receptor inhibited both motility and glycolytic CO2 production, indicating that both processes are receptor mediated.

Effects of long-term hypoxia on enzymes of carbohydrate metabolism in the Gulf killifish, Fundulus grandis.

Abstract: The goal of the current study was to generate a comprehensive, multi-tissue perspective of the effects of chronic hypoxic exposure on carbohydrate metabolism in the Gulf killifish Fundulus grandis. Fish were held at approximately 1.3·mg·l ‐1 dissolved oxygen (~3.6·kPa) for 4·weeks, after which maximal activities were measured for all glycolytic enzymes in four tissues (white skeletal muscle, liver, heart and brain), as well as for enzymes of glycogen metabolism (in muscle and liver) and gluconeogenesis (in liver). The specific activities of enzymes of glycolysis and glycogen metabolism were strongly suppressed by hypoxia in white skeletal muscle, which may reflect decreased energy demand in this tissue during chronic hypoxia. In contrast, several enzyme specific activities were higher in liver tissue after hypoxic exposure, suggesting increased capacity for carbohydrate metabolism. Hypoxic exposure affected fewer enzymes in heart and brain than in skeletal muscle and liver, and the changes were smaller in magnitude, perhaps due to preferential perfusion of heart and brain during hypoxia. The specific activities of some gluconeogenic enzymes increased in liver during long-term hypoxic exposure, which may be coupled to increased protein catabolism in skeletal muscle. These results demonstrate that when intact fish are subjected to prolonged hypoxia, enzyme activities respond in a tissue-specific fashion reflecting the balance of energetic demands, metabolic role and oxygen supply of particular tissues. Furthermore, within glycolysis, the effects of hypoxia varied among enzymes, rather than being uniformly distributed among pathway enzymes.

Switch of glycolysis to gluconeogenesis by dexamethasone for treatment of hepatocarcinoma

Abstract: Hepatocytes use gluconeogenesis to produce glucose, but whether this process is altered in hepatocellular carcinoma (HCC) is unclear. Here, the loss of gluconeogenesis in HCC and altered glucocorticoid regulation is demonstrated and glucocorticoid treatment is shown to reduce tumour burden.