INTERRELATIONSHIPS BETWEEN THE TRICARBOXYLIC ACID AND GLYOXYLATE CYCLES STUDIED WITH BACTERIAL AUXOTROPHS

1962 ◽  
Vol 8 (2) ◽  
pp. 241-247 ◽  
Author(s):  
Henry C. Reeves ◽  
Samuel J. Ajl
Keyword(s):  
Carbon Source ◽  
Sole Carbon Source ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Mineral Salts ◽  
Glyoxylate Bypass ◽  
Acid Cycle ◽  
E Coli ◽  
Acetate Medium ◽  
Metabolic Significance

An autotroph of Escherichia coli, E26-6, which is unable to grow aerobically in a simple mineral-salts medium with either acetate, glutamate, isocitrate, or any one of the C4 dicarboxylic acid intermediates of the tricarboxylic acid cycle as sole carbon source, has been investigated. The mutant is able to grow, however, in a mineral-salts acetate medium supplemented with any one of the above acids. The specific activities of the tricarboxylic acid cycle and glyoxylate bypass enzymes, with the exception of alpha-ketoglutaric dehydrogenase, which is greatly impaired in the auxotroph, were found to be essentially the same in both the parent and the mutant. Thus, the glyoxylate bypass alone is not capable of supplying sufficient C4 intermediates to allow the growth of E. coli on acetate. Further, there appear to be no other metabolic pathways leading to C4 production, which are of major metabolic significance during growth on acetate, other than the tricarboxylic and glyoxylate cycles. Finally, in conjunction with the tricarboxylic acid cycle, the malate synthetase and isocitritase reactions provide a mechanism which enables E. coli to grow on a medium containing acetate as the sole carbon source.

scholarly journals Characteristics of alanine: glyoxylate aminotransferase from Saccharomyces cerevisiae, a regulatory enzyme in the glyoxylate pathway of glycine and serine biosynthesis from tricarboxylic acid-cycle intermediates

1985 ◽  
Vol 231 (1) ◽  
pp. 157-163 ◽  
Author(s):  
Y Takada ◽  
T Noguchi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Carbon Source ◽  
Sole Carbon Source ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Glyoxylate Aminotransferase ◽  
Serine Biosynthesis ◽  
Glyoxylate Pathway

Alanine: glyoxylate aminotransferase (EC 2.6.1.44), which is involved in the glyoxylate pathway of glycine and serine biosynthesis from tricarboxylic acid-cycle intermediates in Saccharomyces cerevisiae, was highly purified and characterized. The enzyme had Mr about 80 000, with two identical subunits. It was highly specific for L-alanine and glyoxylate and contained pyridoxal 5′-phosphate as cofactor. The apparent Km values were 2.1 mM and 0.7 mM for L-alanine and glyoxylate respectively. The activity was low (10 nmol/min per mg of protein) with glucose as sole carbon source, but was remarkably high with ethanol or acetate as carbon source (930 and 430 nmol/min per mg respectively). The transamination of glyoxylate is mainly catalysed by this enzyme in ethanol-grown cells. When glucose-grown cells were incubated in medium containing ethanol as sole carbon source, the activity markedly increased, and the increase was completely blocked by cycloheximide, suggesting that the enzyme is synthesized de novo during the incubation period. Similarity in the amino acid composition was observed, but immunological cross-reactivity was not observed among alanine: glyoxylate aminotransferases from yeast and vertebrate liver.

Utilization of fructose and glutamate by Rhodospirillum rubrum

1968 ◽  
Vol 14 (5) ◽  
pp. 493-498 ◽  
Author(s):  
Margaret S. Gibson ◽  
Chih H. Wang
Keyword(s):  
Carbon Source ◽  
Sole Carbon Source ◽  
Rhodospirillum Rubrum ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Glycolytic Pathway ◽  
Light Conditions ◽  
Acid Cycle

Fructose served as sole carbon source for the growth of Rhodospirillum rubrum anaerobically under light or aerobically in the dark while glucose did not. Glucose was not utilized by the organism at all. Radiorespirometric studies, using 14C specifically labelled fructose as substrate, revealed that fructose is catabolized exclusively via the Embden–Meyerhof–Parnas (EMP) glycolytic pathway. Both L-glutamic and D-glutamic acids can be utilized by this organism, via the tricarboxylic acid cycle (TCA) pathway, under either aerobic-dark or anaerobic-light conditions.

Glucose metabolism and pyruvate excretion by Streptomyces alboniger

1985 ◽  
Vol 31 (8) ◽  
pp. 702-706 ◽  
Author(s):  
Kenneth G. Surowitz ◽  
Robert M. Pfister
Keyword(s):  
Carbon Source ◽  
High Performance ◽  
Sole Carbon Source ◽  
Tricarboxylic Acid Cycle ◽  
Carbon Sources ◽  
Aerial Mycelium ◽  
Tricarboxylic Acid ◽  
Acid Metabolite ◽  
Acid Cycle ◽  
Glycolytic Activity

The formation of aerial mycelia and spores by Streptomyces alboniger has been observed to be inhibited by glucose supplied in the growth medium as the sole carbon source or supplied in combination with other utilizable carbon sources. Analysis of the metabolism of radiolabelled mannose and sucrose in the presence and absence of glucose demonstrated that glucose functions as the preferred carbon source, inhibiting the uptake and oxidation of the sugars within 15 min of its addition. The inhibition of aerial mycelium formation was shown to result from the excretion of an acidic metabolite, and could be overcome by the addition of a buffering system. The acid metabolite was identified as pyruvic acid by high-performance liquid chromatography and by paper chromatography. Acid was not produced in substantial quantities in dextrin broth or in glucose broth supplemented with 5 mM adenine. Analysis of the pathway of pyruvate overproduction demonstrated that growth on glucose resulted in increased glycolytic activity, relative to the activity of the tricarboxylic acid cycle on this substrate, while growth on dextrin or glucose supplemented with 5 mM adenine resulted in balanced glycolytic and tricarboxylic acid cycle activities.

Saccharomyces cerevisiae contains two functional citrate synthase genes

1986 ◽  
Vol 6 (6) ◽  
pp. 1936-1942
Author(s):  
K S Kim ◽  
M S Rosenkrantz ◽  
L Guarente
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Carbon Source ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Nuclear Gene ◽  
Tricarboxylic Acid ◽  
Yeast Genome ◽  
Gene Encoding ◽  
Acid Cycle ◽  
Nonfermentable Carbon Source

The tricarboxylic acid cycle occurs within the mitochondria of the yeast Saccharomyces cerevisiae. A nuclear gene encoding the tricarboxylic acid cycle enzyme citrate synthase has previously been isolated (M. Suissa, K. Suda, and G. Schatz, EMBO J. 3:1773-1781, 1984) and is referred to here as CIT1. We report here the isolation, by an immunological method, of a second nuclear gene encoding citrate synthase (CIT2). Disruption of both genes in the yeast genome was necessary to produce classical citrate synthase-deficient phenotypes: glutamate auxotrophy and poor growth on rich medium containing lactate, a nonfermentable carbon source. Therefore, the citrate synthase produced from either gene was sufficient for these metabolic roles. Transcription of both genes was maximally repressed in medium containing both glucose and glutamate. However, transcription of CIT1 but not of CIT2 was derepressed in medium containing a nonfermentable carbon source. The significance of the presence of two genes encoding citrate synthase in S. cerevisiae is discussed.

THE TRICARBOXYLIC ACID AND GLYOXYLATE CYCLES IN XANTHOMONAS PHASEOLI (XP8)

1959 ◽  
Vol 5 (1) ◽  
pp. 1-8 ◽  
Author(s):  
N. B. Madsen ◽  
R. M. Hochster
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Glyoxylate Cycle ◽  
Sole Source ◽  
Tricarboxylic Acid ◽  
Acid Cycle ◽  
Main Pathway ◽  
The Individual ◽  
Acetate Medium ◽  
Terminal Oxidation ◽  
The Glyoxylate Cycle

Cell-free extracts of Xanthomonas phaseoli contain the individual enzymes of the tricarboxylic acid cycle, and it is suggested that this is the main pathway for the terminal oxidation of carbohydrate in this organism. X. phaseoli can grow on a medium containing acetate as the sole source of carbon. Cell-free extracts of such acetate-grown organisms contain the enzymes of the glyoxylate cycle, and it is concluded that the operation of this cycle permits the initial stages of synthesis of complex cell material from acetate at a rate sufficiently high to account for the observed rate of growth on the acetate medium. The two enzymes required to modify a tricarboxylic acid cycle into a glyoxylate cycle are present in very small amounts (malate synthetase) or absent entirely (isocitritase) in extracts of glucose-grown X. phaseoli.

scholarly journals Disrupting the ArcA regulatory network increases tetracycline susceptibility of TetREscherichia coli

2020 ◽  
Author(s):  
Mario L. Arrieta-Ortiz ◽  
Min Pan ◽  
Amardeep Kaur ◽  
Vivek Srinivas ◽  
Ananya Dash ◽  
...  
Keyword(s):  
Regulatory Network ◽  
Tricarboxylic Acid Cycle ◽  
Physiological State ◽  
Redox Homeostasis ◽  
Tricarboxylic Acid ◽  
Proton Motive Force ◽  
Acid Cycle ◽  
E Coli ◽  
Metabolic Remodeling ◽  
Tetracycline Treatment

ABSTRACTThere is an urgent need for strategies to discover secondary drugs to prevent or disrupt antimicrobial resistance (AMR), which is causing >700,000 deaths annually. Here, we demonstrate that tetracycline resistant (TetR) Escherichia coli undergoes global transcriptional and metabolic remodeling, including down-regulation of tricarboxylic acid cycle and disruption of redox homeostasis, to support consumption of the proton motive force for tetracycline efflux. Targeted knockout of ArcA, identified by network analysis as a master regulator among 25 transcription factors of this new compensatory physiological state, significantly increased the susceptibility of TetRE. coli to tetracycline treatment. A drug, sertraline, which generated a similar metabolome profile as the arcA knockout strain also synergistically re-sensitized TetRE. coli to tetracycline. The potentiating effect of sertraline was eliminated upon knocking out arcA, demonstrating that the mechanism of synergy was through action of sertraline on the tetracycline-induced ArcA network in the TetR strain. Our findings demonstrate that targeting mechanistic drivers of compensatory physiological states could be a generalizable strategy to re-sensitize AMR pathogens to lost antibiotics.

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