Metabolism of mycobacteria

The metabolism of mycobacteria have been studied with reference to carbohydrate, lipids, nitrogen metabolism and oxidative phosphorylation. Some of the enzymes of glycolytic pathway, tricarboxylic acid cycle and lypogenic enzymes were purified, characterized and their kinetic properties investigated. The effect of age of the culture and environmental factors on different aspects of metabolism of mycobacteria were also studied. A comparison of lipid profile in various species of mycobacteria grown in different culture conditions were made. The metabolism of spheroplasts isolated from mycobacteria has been established with respect to their energy charge and to synthesize peptidoglycan using D-alanine as the precursor     

Autophagy

Multidisciplinary approaches are increasingly being used to elucidate the role of autophagy in health and disease and to harness it for therapeutic purposes. The broad range of topics included in the program of the Vancouver Autophagy Symposium (VAS) 2013 illustrated this multidisciplinarity: structural biology of Atg proteins, mechanisms of selective autophagy, in silico drug design targeting ATG proteins, strategies for drug screening, autophagy-metabolism interplay, and therapeutic approaches to modulate autophagy. VAS 2013 took place at the British Columbia Cancer Research Centre, and was hosted by the CIHR Team in Investigating Autophagy Proteins as Molecular Targets for Cancer Treatment. The program was designed as a day of research exchanges, featuring two invited keynote speakers, internationally recognized for their groundbreaking contributions in autophagy, Dr Ana Maria Cuervo (Albert Einstein College of Medicine, Bronx, NY) and Dr Jayanta Debnath (University of California, San Francisco). By bringing together international and local experts in cell biology, drug discovery, and clinical translation, the symposium facilitated rich interdisciplinary discussions focused on multiple forms of autophagy and their regulation and modulation in the context of cancer.     

Archaebacterial Relationships of the Phosphoenolpyruvate Carboxykinase Gene Reveal Mosaicism of Giardia intestinalis Core Metabolism

A gene encoding a putative GTP-specific phosphoenolpyruvate carboxykinase has been cloned and sequenced from the type I amitochondriate protist Giardia intestinalis. The deduced amino acid sequence is related most closely to homologs from hyperthermophilic archaebacteria and only more distantly to homologs from Eubacteria and Metazoa. Most enzymes of Giardia core metabolism, however, are related more closely to eubacterial and metazoan homologs. An archaebacterial relationship has been noted previously for the unusual acetyl-CoA synthetase (ADP-forming) of this organism. The results suggest that phosphoenolpyruvate carboxykinase and acetyl-CoA synthetase have been acquired from different sources than most enzymes of Giardia core metabolism.     

Cloturin: effect on energy-producing processes in Ehrlich ascites and P388 murine leukaemia cells.

The main purpose of the present investigation was to study the effect of cloturin on aerobic glycolysis, endogenous and exogenous respiration and the level of ATP in both Ehrlich ascites carcinoma (EAC) and P388 murine leukaemia cells incubated in vitro. Also its effect on the level of total (T-SH) and non-protein (NP-SH) thiol groups was investigated. A significant inhibition of aerobic glycolysis was found only in P388 cells after 60 min of cloturin action. Cloturin inhibited both endogenous and exogenous respiration of EAC with succinate as substrate. Cloturin decreased the level of ATP after 2 h incubation in both types of tumour cell. The level of NP-SH was decreased more than that of T-SH in both types of cell.     

Aerobic glycolysis of bone and cartilage: The possible involvement of fatty acid oxidation

The apparent paradox of aerobic glycolysis has been investigated in bone and in cartilage. A new cytochemical procedure for hydroxyacyl dehydrogenase (HOAD) activity showed that the maximal activity of this enzyme in both tissues was equivalent to the maximal activity of glyceraldehyde 3-phosphate dehydrogenase (GAPD). The sum of these activities gave a measure of the maximum amount of acetyl-coenzyme A that could be produced. In these tissues, but not in liver which does not exhibit aerobic glycolysis, this summed value exceeded the maximal activity of succinate dehydrogenase (SDH). Consequently, it suggested that where fatty acid oxidation is sufficient to supply all the acetyl-coenzyme A required for the Krebs' cycle, that derived from fatty acid oxidation may inhibit pyruvate dehydrogenase causing accumulation of pyruvate which must be converted to lactate if pentose-shunt activity is to be maintained.     

Relationship of Cellular Energetics to RNA Metabolism in Tetrahymena pyriformis W.*

Cultures of Tetrahymena pyriformis in a non-nutrient buffer degrade RNA and excrete hypoxanthine, uracil and orthophosphate. Glucose addition leads to the retention of a portion of the purine, pyrimidine, and orthophosphate by the cells; however, the hexose has little influence on the RNA level. Acetate supplementation has no effect on RNA degradation or on the distribution of the catabolic products between the cells and the environment. Interruption of oxidative phosphorylation by 2,4-dinitrophenol results in an increase in RNA degradation. This action is annulled by the glycolytic substrate, glucose, but not by acetate. A combination of iodoacetic acid and glucose blocks glycolysis and increases cellular RNA loss which can be reversed by the addition of the citric acid cycle substrate, acetate. These findings suggest that the available cellular energy supply in starved cells is sufficient to regulate the rate of RNA degradation. Disruption of ATP generation by the appropriate inhibitors, however, allows the demonstration of the importance of energy-yielding reactions in the determination of the amount of nucleic acid loss. It appears that glycolysis and oxidative phosphorylation are equally efficient in sustaining the regulatory process. RNA synthesis during starvation conditions is a discontinuous process with a sharp rate change after 30 min of incubation. 2,4-Dinitrophenol inhibits [2-¹⁴C] uracil incorporation into the nucleic acid. Glucose does not annul the inhibition of synthesis in contrast to the influence of the hexose on RNA degradation. This observation demonstrates that the synthetic and degradative processes are not directly coupled. Glycogen synthesis and RNA degradation appear to compete for the available energy supply and respond in a similar fashion to the metabolic inhibitors and carbon sources.     

Effects of tumor necrosis factor (TNF) on lipolytic activities of rat heart

Summary Tumor Necrosis Factor (TNF) inhibits lipoprotein lipase activity in cultured myocytes and in the Langendorff rat heart after 3 h perfusion with TNF of glucocorticoid-pretreated rats. TNF acutely stimulates glyc(ogen)olysis and concomitantly endogenous lipolysis. The latter was significantly increased only when rats had been pretreated with glucocorticoid or fed a trierucate-rich diet. Under these conditions, contractile activity of the Langendorff hearts was acutely increased by TNF The mechanism of the actue increase of contractile function and the accompanying increased glycolytic and lipolytic activities, by TNF, may be explained by increased cytosolic Ca²⁺ and cAMP levels.     

PDK4 dictates metabolic resistance to ferroptosis by suppressing pyruvate oxidation and fatty acid synthesis

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