scholarly journals Tricarboxylic acid-cycle and related enzymes in restricted facultative methylotrophs

1975 ◽  
Vol 148 (3) ◽  
pp. 505-511 ◽  
Author(s):  
J Colby ◽  
L J Zatman
Keyword(s):  
Succinate Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Isocitrate Dehydrogenase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Methylotrophic Bacteria ◽  
Acid Cycle ◽  
Oxoglutarate Dehydrogenase ◽  
Specific Activities ◽  
Succinyl Coa Synthetase

The isolation is described of pure cultures of three non-methane-utilizing methylotrophic bacteria which, together with the previously described Bacillus PM6, have a very limited range of growth substrates; these organisms are designated “restricted facultative’ methylotrophs. Two of these isolates, W6A and W3A1, grow only on glucose out of 50 non-C1 compounds tested, whereas the third isolate S2A1 and Bacillus PM6 grow on betaine, glucose, gluconate, alanine, glutamate, citrate and nutrient agar, but not on any of a further 56 non-C1 compounds. Crude sonic extracts of trimethylamine-grown and glucose-grown W6A and W3A1 isolates, and of trimethylamine-grown C2A1 (an obligate methylotroph) contain (i) no detectable 2-oxogltarate dehydrogenase activity, (ii) very low or zero specific activities of succinate dehydrogenase and succinyl-CoA synthetase and (iii) NAD+-dependent isocitrate dehydrogenase activity. Extracts of trimethylamine-grown PM6 and S2A1 methylotrophs have (i) very low 2-oxoglutarate dehydrogenase specific activities, (ii) comparatively high specific activities of succinate dehydrogenase, malate dehydrogenase and succinyl-CoA synthetase and (iii) NADP+-dependent isocitrate dehydrogenase activity but no NAD+-dependent isocitrate dehydrogenase activity. The activities of most of these enzymes are increased during growth on glucose, alanine, glutamate or citrate, but only very low 2-oxoglutarate dehydrogenase activities are present under all growth conditions. The restricted facultative methylotrophs grow on certain non-C1 compounds in the absence of 2-oxoglutarate dehydrogenase and, in some cases, of other enzymes of the tricarboxylic acid cycle; these lesions cannot therefore be the sole cause of obligate methylotrophy.

Tricarboxylic Acid Cycle Enzymes of the Ectomycorrhizal Basidiomycete, Suillus bovinus

2001 ◽  
Vol 56 (5-6) ◽  
pp. 334-342 ◽  
Author(s):  
Norbert Grotjohann ◽  
Yi Huangb ◽  
Wolfgang Kowallik
Keyword(s):  
Succinate Dehydrogenase ◽  
Malate Dehydrogenase ◽  
Isocitrate Dehydrogenase ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Technical Problems ◽  
Acid Cycle ◽  
Suillus Bovinus ◽  
Cell Extracts

In crude cell extracts of the ectomycorrhizal fungus, Suillus bovinus, activities of citrate synthase, aconitase, isocitrate dehydrogenase, succinate dehydrogenase, fumarase, and malate dehydrogenase have been proved and analyzed. Citrate synthase exhibited high affinities for both its substrates: oxaloacetate (Km = 0.018 mᴍ) and acetyl-CoA (Km = 0.014 mᴍ) . Aconitase showed better affinity for isocitrate (Km = 0.62 mᴍ) than for citrate (Km = 3.20 mᴍ) . Analysis of isocitrate dehydrogenase revealed only small maximum activity (60 nmol x mg protein-1 x min -1), the enzyme being exclusively NADP+-dependent. Using the artificial electron acceptor dichlorophenol indophenol, activity and substrate affinity of succinate dehydrogenase were rather poor. Fumarase proved Fe2+-independent. Its affinity for malate was found higher ( Km = 1.19 mᴍ) than that for fumarate ( Km = 2.09 mᴍ) . High total activity of malate dehydrogenase could be separated by native PAGE into a slowly running species of (mainly) cytosolic (about 80%) and a faster running species of (mainly) mitochondrial origin. Affinities for oxaloacetate of the two enzyme species were found identical within limits of significance (Km = 0.24 mᴍ and 0.22 mᴍ) . The assumed cytosolic enzyme exhibited affinity for malate (Km = 5.77 mᴍ) more than one order of magnitude lower than that for oxaloacetate. FPLC on superose 12 revealed only one activity band at a molecular mass of 100 ± 15 kDa. Activities of 2-oxoglutarate dehydrogenase and of succinyl-CoA synthetase could not be found. Technical problems in their detection, but also existence of an incomplete tricarboxylic acid cycle are considered. Metabolite affinities, maximum activities and pʜ-dependences of fumarase and of malate dehydrogenase allow the assumption of a reductive instead of oxidative function of these enzymes in vivo.

scholarly journals Tricarboxylic acid cycle and proton gradient in Pandoravirus massiliensis: Is it still a virus?

2020 ◽  
Author(s):  
Sarah Aherfi ◽  
Djamal Brahim Belhaouari ◽  
Lucile Pinault ◽  
Jean-Pierre Baudoin ◽  
Philippe Decloquement ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Isocitrate Dehydrogenase ◽  
Energy Production ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Proton Gradient ◽  
Giant Virus ◽  
Acid Cycle ◽  
Key Enzyme

ABSTRACTSince the discovery of Acanthamoeba polyphaga Mimivirus, the first giant virus of amoeba, the historical hallmarks defining a virus have been challenged. Giant virion sizes can reach up to 2.3 µm, making them visible by optical microscopy. They have large genomes of up to 2.5 Mb that encode proteins involved in the translation apparatus. Herein, we investigated possible energy production in Pandoravirus massiliensis, the largest of our giant virus collection. MitoTracker and TMRM mitochondrial membrane markers allowed for the detection of a membrane potential in virions that could be abolished by the use of the depolarizing agent CCCP. An attempt to identify enzymes involved in energy metabolism revealed that 8 predicted proteins of P. massiliensis exhibited low sequence identities with defined proteins involved in the universal tricarboxylic acid cycle (acetyl Co-A synthase; citrate synthase; aconitase; isocitrate dehydrogenase; α-ketoglutarate decarboxylase; succinate dehydrogenase; fumarase). All 8 viral predicted ORFs were transcribed together during viral replication, mainly at the end of the replication cycle. Two of these proteins were detected in mature viral particles by proteomics. The product of the ORF132, a predicted protein of P. massiliensis, cloned and expressed in Escherichia coli, provided a functional isocitrate dehydrogenase, a key enzyme of the tricarboxylic acid cycle, which converts isocitrate to α-ketoglutarate. We observed that membrane potential was enhanced by low concentrations of Acetyl-CoA, a regulator of the tricarboxylic acid cycle. Our findings show for the first time that energy production can occur in viruses, namely, pandoraviruses, and the involved enzymes are related to tricarboxylic acid cycle enzymes. The presence of a proton gradient in P. massiliensis coupled with the observation of genes of the tricarboxylic acid cycle make this virus a form a life for which it is legitimate to question ‘what is a virus?’.

scholarly journals Succinate Dehydrogenase Loss in Familial Paraganglioma: Biochemistry, Genetics, and Epigenetics

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Yeng F. Her ◽  
L. James Maher
Keyword(s):  
Succinate Dehydrogenase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Atp Production ◽  
Metabolic Defects ◽  
Biochemical Genetic

It is counterintuitive that metabolic defects reducing ATP production can cause, rather than protect from, cancer. Yet this is precisely the case for familial paraganglioma, a form of neuroendocrine malignancy caused by loss of succinate dehydrogenase in the tricarboxylic acid cycle. Here we review biochemical, genetic, and epigenetic considerations in succinate dehydrogenase loss and present leading models and mysteries associated with this fascinating and important tumor.

scholarly journals Role of Phosphoenolpyruvate in the NADP-Isocitrate Dehydrogenase and Isocitrate Lyase Reaction in Escherichia coli

2006 ◽  
Vol 189 (3) ◽  
pp. 1176-1178 ◽  
Author(s):  
Tadashi Ogawa ◽  
Keiko Murakami ◽  
Hirotada Mori ◽  
Nobuyoshi Ishii ◽  
Masaru Tomita ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Isocitrate Dehydrogenase ◽  
Isocitrate Lyase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Glyoxylate Shunt ◽  
Acid Cycle ◽  
Uncompetitive Inhibition

ABSTRACT Phosphoenolpyruvate inhibited Escherichia coli NADP-isocitrate dehydrogenase allosterically (Ki of 0.31 mM) and isocitrate lyase uncompetitively (Ki ′ of 0.893 mM). Phosphoenolpyruvate enhances the uncompetitive inhibition of isocitrate lyase by increasing isocitrate, which protects isocitrate dehydrogenase from the inhibition, and contributes to the control through the tricarboxylic acid cycle and glyoxylate shunt.

scholarly journals Maximum activities of some enzymes of glycolysis, the tricarboxylic acid cycle and ketone-body and glutamine utilization pathways in lymphocytes of the rat

1982 ◽  
Vol 208 (3) ◽  
pp. 743-748 ◽  
Author(s):  
M. Salleh M. Ardawi ◽  
Eric A. Newsholme
Keyword(s):  
Ketone Body ◽  
Citrate Synthase ◽  
Ketone Bodies ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Maximum Activity ◽  
Graft Versus Host Reaction ◽  
Acid Cycle ◽  
Oxoglutarate Dehydrogenase

1. The maximum activity of hexokinase in lymphocytes is similar to that of 6-phosphofructokinase, but considerably greater than that of phosphorylase, suggesting that glucose rather than glycogen is the major carbohydrate fuel for these cells. Starvation increased slightly the activities of some of the glycolytic enzymes. A local immunological challenge in vivo (a graft-versus-host reaction) increased the activities of hexokinase, 6-phosphofructokinase, pyruvate kinase and lactate dehydrogenase, confirming the importance of the glycolytic pathway in cell division. 2. The activities of the ketone-body-utilizing enzymes were lower than those of hexokinase or 6-phosphofructokinase, unlike in muscle and brain, and were not affected by starvation. It is suggested that the ketone bodies will not provide a quantitatively important alternative fuel to glucose in lymphocytes. 3. Of the enzymes of the tricarboxylic acid cycle whose activities were measured, that of oxoglutarate dehydrogenase was the lowest, yet its activity (about 4.0μmol/min per g dry wt. at 37°C) was considerably greater than the flux through the cycle (0.5μmol/min per g calculated from oxygen consumption by incubated lymphocytes). The activity was decreased by starvation, but that of citrate synthase was increased by the local immunological challenge in vivo. It is suggested that the rate of the cycle would increase towards the capacity indicated by oxoglutarate dehydrogenase in proliferating lymphocytes. 4. Enzymes possibly involved in the pathway of glutamine oxidation were measured in lymphocytes, which suggests that an aminotransferase reaction(s) (probably aspartate aminotransferase) is important in the conversion of glutamate into oxoglutarate rather than glutamate dehydrogenase, and that the maximum activity of glutaminase is markedly in excess of the rate of glutamine utilization by incubated lymphocytes. The activity of glutaminase is increased by both starvation and the local immunological challenge in vivo. This last finding suggests that metabolism of glutamine via glutaminase is important in proliferating lymphocytes.

scholarly journals Stimulation of [1-14C]oleate oxidation to 14CO2 in isolated rat hepatocytes by the catecholamines, vasopressin and angiotensin. A possible mechanism of action

1983 ◽  
Vol 212 (1) ◽  
pp. 85-91 ◽  
Author(s):  
M C Sugden ◽  
D I Watts
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Tricarboxylic Acid Cycle ◽  
Rat Hepatocytes ◽  
Tricarboxylic Acid ◽  
Isolated Rat Hepatocytes ◽  
Acid Cycle ◽  
14Co2 Production ◽  
Oxoglutarate Dehydrogenase ◽  
Stimulation Of

Adrenaline, noradrenaline, vasopressin and angiotensin increased 14CO2 production from [1-14C]oleate by hepatocytes from fed rats but not by hepatocytes from starved rats. The hormones did not increase 14CO2 production when hepatocytes from fed rats were depleted of glycogen in vitro. Increased 14CO2 production from]1-14C]oleate in response to the hormones was observed when hepatocytes from starved rats were incubated with 3-mercaptopicolinate, an inhibitor of phosphoenolpyruvate carboxykinase. 3-Mercaptopicolinate inhibited uptake and esterification of [1-14C]oleate, slightly increased 14CO2 production from [1-14C]oleate and greatly increased the [3-hydroxybutyrate]/[acetoacetate] ratio. In the presence of 3-mercaptopicolinate 14CO2 production in response to the catecholamines was blocked by the α-antagonist phentolamine and required extracellular Ca2+. The effects of vasopressin and angiotensin were also Ca2+-dependent. The actions of the hormones of 14CO2 production from [I-14C]oleate by hepatocytes from starved rats in the presence of 3-mercaptopicolinate thus have the characteristics of the response to the hormones found with hepatocytes from fed rats incubated without 3-mercaptopicolinate. The stimulatory effects of the hormones on 14CO2 production from [1-14C]oleate were not the result of decreased esterification (as the hormones increased esterification) or increased β-oxidation. It is suggested that the effect of the hormones to increase 14CO2 production from [1-14C]oleate are mediated by CA2+-activation of NAD+-linked isocitrate dehydrogenase, the 2-oxoglutarate dehydrogenase complex, and/or electron transport. The results also demonstrate that when the supply of oxaloacetate is limited it is utilized for gluconeogenesis rather than to maintain tricarboxylic acid-cycle flux.

scholarly journals The pathway of glycollate utilization in Chlorella pyrenoidosa

1970 ◽  
Vol 117 (5) ◽  
pp. 929-937 ◽  
Author(s):  
J. M. Lord ◽  
M. J. Merrett
Keyword(s):  
Soluble Fraction ◽  
Tricarboxylic Acid Cycle ◽  
Experimental Period ◽  
Chlorella Pyrenoidosa ◽  
Total Radioactivity ◽  
Tricarboxylic Acid ◽  
Short Term ◽  
Acid Cycle ◽  
Metabolic Sequence ◽  
Specific Activities

1. Exogenous glycollate was rapidly metabolized in both the light and the dark by photoautotrophically grown Chlorella pyrenoidosa. 2. The incorporation of 14C from [1-14C]glycollate by these cells was inhibited by the tricarboxylic acid-cycle inhibitors monofluoroacetate, diethylmalonate and arsenite, and also by α-hydroxypyrid-2-ylmethanesulphonate and isonicotinylhydrazine. 3. Short-term kinetic experiments showed over 80% of the total 14C present in the soluble fraction from the cells to be in glycine and serine after 10s. This percentage decreased with time whereas the percentage radioactivity in glycerate increased for up to 30s then remained steady. The percentage of the total radioactivity present in citrate increased over the experimental period. Malate was the only other tricarboxylic acid-cycle intermediate to become labelled. 4. The kinetic and inhibitor experiments supported the following pathway of glycollate incorporation: glycollate → glyoxylate → glycine → serine → hydroxypyruvate → glycerate → 3-phosphoglycerate → 2-phosphoglycerate → phosphoenolpyruvate → pyruvate → acetyl-CoA. 5. The specific activities of the enzymes catalysing this metabolic sequence in cell-free extracts were great enough to account for the observed rate of glycollate metabolism of 0.25μmol/h per mg dry wt. of cells in the light.

SOME METABOLIC EFFECTS OF ADENOVIRUS INFECTION IN HELA CELLS

1957 ◽  
Vol 3 (7) ◽  
pp. 1015-1020 ◽  
Author(s):  
K. R. Rozee ◽  
L. J. Ottey ◽  
C. E. van Rooyen
Keyword(s):  
Lactic Acid ◽  
Dehydrogenase Activity ◽  
Hela Cells ◽  
Glucose Utilization ◽  
Tricarboxylic Acid Cycle ◽  
Lactic Dehydrogenase ◽  
Tricarboxylic Acid ◽  
Metabolic Effects ◽  
Adenovirus Infection ◽  
Acid Cycle

HeLa cells infected with type 7 adenovirus produced amounts of lactic acid in excess of those produced by uninfected HeLa cells, as has been found with other adenovirus types. It was found that the increased rate of glucose utilization and higher lactic dehydrogenase activity in adenovirus-infected HeLa cells could partially explain this phenomenon. It is suggested that the terminal degradative mechanisms are more active in adenovirus-infected HeLa cells and that an operative tricarboxylic acid cycle is necessary for optimum replication of type 7 adenovirus.

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