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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transcription of fatty acid synthase (FAS) and malic enzyme (ME) in avian liver is low during starvation or feeding a low-carbohydrate, high-fat diet and high during feeding a high-carbohydrate, low-fat diet. The role of glucose in the nutritional control of FAS and ME was investigated by determining the effects of this metabolic fuel on expression of FAS and ME in primary cultures of chick embryo hepatocytes. In the presence of triiodothyronine, glucose (25 mM) stimulated an increase in the activity and mRNA abundance of FAS and ME. These effects required the phosphorylation of glucose to glucose 6-phosphate but not further metabolism downstream of the aldolase step of the glycolytic pathway. Xylitol mimicked the effects of glucose on FAS and ME expression, suggesting that an intermediate of the pentose phosphate pathway may be involved in mediating this response. The effects of glucose on the mRNA abundance of FAS and ME were accompanied by similar changes in transcription of FAS and ME. These data support the hypothesis that glucose plays a role in mediating the effects of nutritional manipulation on transcription of FAS and ME in liver.
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PMID:Glucose stimulates transcription of fatty acid synthase and malic enzyme in avian hepatocytes. 953 Jan 33

We have previously shown that stress-induced protein degradation requires a functional ubiquitin-activating enzyme and the autophagic-lysosomal pathway. In this study, we examined the occurrence of ubiquitin-protein conjugates that form during nutrient starvation. Kidney and liver epithelial cells respond to nutrient stress by enhancing autophagy and protein degradation. We have shown that this degradative response was more dramatic in nondividing cultures. In addition, the onset of autophagy was suppressed by pactamycin, cycloheximide, and puromycin. We observed an accumulation of ubiquitinated proteins coincident with the degradative response to amino acid starvation. The stress-induced protein ubiquitination was not affected by cycloheximide, indicating that protein synthesis was not required. The ubiquitinated proteins were localized to the cytosol and subcellular fractions enriched with autophagosomes and lysosomes. The incorporation of the ubiquitinated proteins into autolysosomes was dramatically reduced by 3-methyladenine, an inhibitor of autophagy. The evidence suggests that ubiquitinated proteins are sequestered by autophagy for degradation. We next set out to identify those primary ubiquitinated proteins at 60 kDa and 68 kDa. Polyclonal antibodies were prepared against these proteins that had been immunopurified from rat liver lysosomes. The antibodies prepared against those 68 kDa proteins also recognized a 40 kDa protein in cytosolic fractions. Internal amino acid sequences obtained from two cyanogen bromide fragments of this 40 kDa protein were shown to be identical to sequences in liver fructose1,6-bisphosphate aldolase B. Anti-Ub68 antibodies recognized purified aldolase A and aldolase B. Conversely, antibodies prepared against aldolase B recognized the 40 kDa aldolase as well as four to five high molecular weight forms, including a 68 kDa protein. Finally, we have shown that the degradation of aldolase B was enhanced during amino acid and serum starvation. This degradation was suppressed by chloroquine and 3-methyladenine, suggesting that aldolase B was being degraded within autolysosomes. We propose that aldolase B is ubiquitinated within the cytosol and then transported into autophagosomes and autolysosomes for degradation during nutrient stress.
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PMID:Ubiquitinated aldolase B accumulates during starvation-induced lysosomal proteolysis. 988 86

We have used two-dimensional electrophoresis (2-DE) to analyze changes in protein expression profiles during a microbial cultivation process on an industrial scale. An Escherichia coli strain W31 10 containing the gene for recombinant human growth hormone production was used. Samples were taken at time intervals ranging from fast to slow growth rate (late growth phase at high cell density/starvation) and 2-DE analysis combined with image analysis using the PDQuest software showed significant alterations in expression levels of a number of proteins. Twenty-four protein spots were identified using a combination of matching with SWISS-2DPAGE E. coli map, N-terminal sequence analysis and mass spectrometry matrix-assisted laser desorption/ionization (MALDI). Two of the most abundant proteins expressed at late growth phase (pI 5.4/28 kDa and pI 5.5/28 kDa) were subjected to N-terminal sequence analysis after electrotransfer of the proteins from a preparative 2-DE gel to polyvinylidene difluoride (PVDF) membrane. Sequence tags of five amino acids in combination with approximate pI and Mr identified both proteins as deoxyribose phosphate aldolase (gene name deoC). In addition, both spots were subjected to tryptic in-gel digestion and analyzed using MALDI. Peptide mass fingerprints from both spots showed similar MALDI spectra and 10 of 10 tryptic fragments confirmed the identity as deoC. The identification of the acidic variant of deoC on 2-DE gels and the observation of this variant as induced during late growth phase is novel.
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PMID:Characterization of periplasmic Escherichia coli protein expression at high cell densities. 1034 49

The Escherichia coli eda gene, which encodes the Entner-Doudoroff aldolase, is central to the catabolism of several sugar acids. Here, we show that Eda synthesis is induced by growth on gluconate, glucuronate, or methyl-beta-D-glucuronide; phosphate limitation; and carbon starvation. Transcription of eda initiates from three promoters, designated P1, P2, and P4, each of which is responsible for induction under different growth conditions. P1 controls eda induction on gluconate and is regulated by GntR. P2 controls eda induction on glucuronate and galacturonate and is regulated by KdgR. P4 is active under conditions of phosphate starvation and is directly controlled by PhoB. In addition, CsrA activates Eda synthesis, apparently by an indirect mechanism that may be involved in the modest changes in expression level that are associated with carbon starvation. The complex regulation of eda is discussed with respect to its several physiological roles, which apparently accommodate not only sugar acid catabolism but also detoxification of metabolites that could accumulate during starvation-induced stress.
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PMID:Multiple regulators control expression of the Entner-Doudoroff aldolase (Eda) of Escherichia coli. 1565 77

Under nitrogen (ammonia)-limited continuous culture conditions, the ruminal anaerobe Selenomonas ruminantium was grown at various dilution rates (D). The proportion of the population that was viable increased with D, being 91% at D = 0.5 h. Washed cell suspensions were subjected to long-term nutrient starvation at 39 degrees C. All populations exhibited logarithmic linear declines in viability that were related to the growth rate. Cells grown at D = 0.05, 0.20, and 0.50 lost about 50% viability after 8.1, 4.6, and 3.6 h, respectively. The linear rates of decline in total cell numbers were dramatically less and constant regardless of dilution rate. All major cell constituents declined during starvation, with the rates of decline being greatest with RNA, followed by DNA, carbohydrate, cell dry weight, and protein. The rates of RNA loss increased with cells grown at higher D values, whereas the opposite was observed for rates of carbohydrate losses. The majority of the degraded RNA was not catabolized but was excreted into the suspending buffer. At all D values, S. ruminantium produced mainly lactate and lesser amounts of acetate, propionate, and succinate during growth. With starvation, only small amounts of acetate were produced. Addition of glucose, vitamins, or both to the suspending buffer or starvation in the spent culture medium resulted in greater losses of viability than in buffer alone. Examination of extracts made from starving cells indicated that fructose diphosphate aldolase and lactate dehydrogenase activities remained relatively constant. Both urease and glutamate dehydrogenase activities declined gradually during starvation, whereas glutamine synthetase activity increased slightly. The data indicate that nitrogen (ammonia)-limited S. ruminantium cells have limited survival capacity, but this capacity is greater than that found previously with energy (glucose)-limited cells. Apparently no one cellular constituent serves as a catabolic substrate for endogenous metabolism. Relative to losses in viability, cellular enzymes are stable, indicating that nonviable cells maintain potential metabolic activity and that generalized, nonspecific enzyme degradation is not a major factor contributing to viability loss.
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PMID:Changes in Viability, Cell Composition, and Enzyme Levels During Starvation of Continuously Cultured (Ammonia-Limited) Selenomonas ruminantium. 1634 16

This investigation addresses the following question: what are the important factors for maintenance of a high catabolic capacity under various starvation conditions? Saccharomyces cerevisiae was cultured in aerobic batch cultures, and during the diauxic shift cells were transferred and subjected to 24 h of starvation. The following conditions were used: carbon starvation, nitrogen starvation in the presence of glucose or ethanol, and both carbon starvation and nitrogen starvation. During the starvation period changes in biomass composition (including protein, carbohydrate, lipid, and nucleic acid contents), metabolic activity, sugar transport kinetics, and the levels of selected enzymes were recorded. Subsequent to the starvation period the remaining catabolic capacity was measured by addition of 50 mM glucose. The results showed that the glucose transport capacity is a key factor for maintenance of high metabolic capacity in many, but not all, cases. The results for cells starved of carbon, carbon and nitrogen, or nitrogen in the presence of glucose all indicated that the metabolic capacity was indeed controlled by the glucose transport ability, perhaps with some influence of hexokinase, phosphofructokinase, aldolase, and enolase levels. However, it was also demonstrated that there was no such correlation when nitrogen starvation occurred in the presence of ethanol instead of glucose.
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PMID:Effect of nutrient starvation on the cellular composition and metabolic capacity of Saccharomyces cerevisiae. 1754 28

Metabolic flux analysis indicated that the heterofermentative Lactobacillus reuteri strain ATCC 55730 uses both the Embden-Meyerhof pathway (EMP) and phosphoketolase pathway (PKP) when glucose or sucrose is converted into the three-carbon intermediate stage of glycolysis. In all cases studied, the main flux is through the PKP, while the EMP is used as a shunt. In the exponential growth phase, 70%, 73%, and 84% of the flux goes through the PKP in cells metabolizing (i) glucose plus fructose, (ii) glucose alone, and (iii) sucrose alone, respectively. Analysis of the genome of L. reuteri ATCC 55730 confirmed the presence of the genes for both pathways. Further evidence for the simultaneous operation of two central carbon metabolic pathways was found through the detection of fructose-1,6-bisphosphate aldolase, phosphofructokinase, and phosphoglucoisomerase activities and the presence of phosphorylated EMP and PKP intermediates using in vitro 31P NMR. The maximum specific growth rate and biomass yield obtained on glucose were twice as low as on sucrose. This was the result of low ATP levels being present in glucose-metabolizing cells, although the ATP production flux was as high as in sucrose-metabolizing cells due to a twofold increase of enzyme activities in both glycolytic pathways. Growth performance on glucose could be improved by adding fructose as an external electron acceptor, suggesting that the observed behavior is due to a redox imbalance causing energy starvation.
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PMID:Phosphoketolase pathway dominates in Lactobacillus reuteri ATCC 55730 containing dual pathways for glycolysis. 1796 51

The survival and behavior of Cupriavidus metallidurans strain CH34 were tested in space. In three spaceflight experiments, during three separate visits to the 'International Space Station' (ISS), strain CH34 was grown for 10-12 days at ambient temperature on mineral agar medium. Space- and earth-grown cells were compared post-flight by flow cytometry and using 2D-gel protein analysis. Pre-, in- and post-flight incubation conditions and experiment design had a significant impact on the survival and growth of CH34 in space. In the CH34 cells returning from spaceflight, 16 proteins were identified which were present in higher concentration in cells developed in spaceflight conditions. These proteins were involved in a specific response of CH34 to carbon limitation and oxidative stress, and included an acetone carboxylase subunit, fructose biphosphate aldolase, a DNA protection during starvation protein, chaperone protein, universal stress protein, and alkyl hydroperoxide reductase. The reproducible observation of the over-expression of these same proteins in multiple flight experiments, indicated that the CH34 cells could experience a substrate limitation and oxidative stress in spaceflight where cells and substrates are exposed to lower levels of gravity and higher doses of ionizing radiation. Bacterium C. metallidurans CH34 was able to grow normally under spaceflight conditions with very minor to no effects on cell physiology, but nevertheless specifically altered the expression of a few proteins in response to the environmental changes.
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PMID:The response of Cupriavidus metallidurans CH34 to spaceflight in the international space station. 1957 10

This study provides first-hand proteomic data on the survival strategy of Anabaena sp. PCC 7120 when subjected to long-term iron-starvation conditions. 2D-gel electrophoresis followed by MALDI-TOF/MS analysis of iron-deficient Anabaena revealed significant and reproducible alterations in ten proteins, of which six are associated with photosynthesis and respiration, three with the antioxidative defense system, and the last, hypothetical protein all1861, conceivably connected with iron homeostasis. Iron-starved Anabaena registered a reduction in growth, photosynthetic pigments, PSI, PSII, whole-chain electron transport, carbon and nitrogen fixation, and ATP and NADPH content. The kinetics of hypothetical protein all1861 expression, with no change in expression until day 3, maximum expression on the 7th day, and a decline in expression from the 15th day onward, coupled with in silico analysis, suggested its role in iron sequestration and homeostasis. Interestingly, the up-regulated FBP-aldolase, Mn/Fe-SOD, and all1861 all appear to assist the survival of Anabeana subjected to iron-starvation conditions. Furthermore, the N2-fixation capabilities of the iron-starved Anabaena encourage us to recommend its application as a biofertilizer, particularly in iron-limited paddy soils.
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PMID:Iron starvation-induced proteomic changes in Anabaena (Nostoc) sp. PCC 7120: exploring survival strategy. 2136 95

Lemna aldolase has been purified by ion-exchange and affinity chromatography. The enzyme is inhibited by pyridoxal phosphate in a manner which suggests that pyridoxal phosphate forms a non-covalent complex with the enzymes which is in equilibrium with the Schiff base covalently modified enzyme. The kinetics of the reversal of inhibition have been used to test the proposition that the fall in aldolase activity observed during periods of nitrogen starvation is due to inhibition by pyridoxal phosphate. It is concluded that the in vivo loss of aldolase activity is not due to pyridoxal phosphate and that the in vitro inhibition of glycolytic enzymes by pyridoxal phosphate is due to the reaction with lysine residues at the active sites which are necessary to bind the strongly acidic sugar phosphates.
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PMID:The effect of pyridoxal phosphate on the activity of aldolase from Lemna minor L. 2442 Jun 64


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