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

Two novel procedures have been used to regulate, in vivo, the formation of phosphoenolpyruvate (PEP) from glycolysis in Streptococcus lactis ML3. In the first procedure, glucose metabolism was specifically inhibited by p-chloromercuribenzoate. Autoradiographic and enzymatic analyses showed that the cells contained glucose 6-phosphate, fructose 6-phosphate, fructose-1,6-diphosphate, and triose phosphates. Dithiothreitol reversed the p-chloromercuribenzoate inhibition, and these intermediates were rapidly and quantitatively transformed into 3- and 2-phosphoglycerates plus PEP. The three intermediates were not further metabolized and constituted the intracellular PEP potential. The second procedure simply involved starvation of the organisms. The starved cells were devoid of glucose 6-phosphate, fructose 6-phosphate, fructose- 1,6-diphosphate, and triose phosphates but contained high levels of 3- and 2-phosphoglycerates and PEP (ca. 40 mM in total). The capacity to regulate PEP formation in vivo permitted the characterization of glucose and lactose phosphotransferase systems in physiologically intact cells. Evidence has been obtained for "feed forward" activation of pyruvate kinase in vivo by phosphorylated intermediates formed before the glyceraldehyde-3-phosphate dehydrogenase reaction in the glycolytic sequence. The data suggest that pyruvate kinase (an allosteric enzyme) plays a key role in the regulation of glycolysis and phosphotransferase system functions in S. lactis ML3.
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PMID:In vivo regulation of glycolysis and characterization of sugar: phosphotransferase systems in Streptococcus lactis. 10 23

Genes of higher eucaryotic cells are considered to show only a limited response to nutritional stress. Here we show, however, that omission of a single essential amino acid from the medium caused a marked rise in the mRNA levels of c-myc, c-jun, junB and c-fos oncogenes and ornithine decarboxylase (ODC) in CHO cells. There was no general accumulation of mRNAs in amino acid-starved cells, since the gamma-actin, beta-tubulin, protein kinase C, RNA polymerase II, and glyceraldehyde-3-phosphate dehydrogenase mRNAs and the total poly(A)+ mRNA were not increased. The levels of c-myc, ODC, and c-jun mRNAs were elevated more by amino acid starvation than by inhibition of protein synthesis with cycloheximide, which is known to increase the levels of these mRNAs. Importantly, however, cycloheximide present during amino acid starvation reduced the rise in the levels of the mRNAs down to the level obtained with cycloheximide alone. This implies that protein synthesis is required for the accumulation of c-myc, ODC, and c-jun mRNAs in amino acid-deprived cells. The junB and c-fos mRNAs, instead, were increased to the same extent or less by amino acid starvation than by cycloheximide treatment. The accumulation of the c-myc mRNA in amino acid-starved cells was due to both stabilization of the mRNA and increase of its transcription. The rise in the c-jun mRNA level seemed to be caused merely by stabilization of the mRNA. Further, despite the inhibition of general protein synthesis, amino acid starvation led to an increase in the synthesis of c-myc polypeptide. The results suggest that mammalian cells have a specific mechanism for registering shortages of amino acids in order to make adjustments compatible with cellular growth.
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PMID:Deprivation of a single amino acid induces protein synthesis-dependent increases in c-jun, c-myc, and ornithine decarboxylase mRNAs in Chinese hamster ovary cells. 212 33

The decreased response of the energy metabolism of lactose-starved Streptococcus cremoris upon readdition of lactose is caused by a decrease of the glycolytic activity (B. Poolman, E. J. Smid, and W. N. Konings, J. Bacteriol. 169:1460-1468, 1987). The decrease in glycolysis is accompanied by a decrease in the activities of glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate mutase. The steady-state levels of pathway intermediates upon refeeding with lactose after various periods of starvation indicate that the decreased glycolysis is primarily due to diminished glyceraldehyde-3-phosphate dehydrogenase activity. Furthermore, quantification of the control strength exerted by glyceraldehyde-3-phosphate dehydrogenase on the overall activity of the glycolytic pathway shows that this enzyme can be significantly rate limiting in nongrowing cells.
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PMID:Control of glycolysis by glyceraldehyde-3-phosphate dehydrogenase in Streptococcus cremoris and Streptococcus lactis. 282 52

1. The ratio [ATP]/[ADP][P(i)], as measured by direct determination of the three components in rat liver, was found in various nutritional states to have approximately the same value as the ratio [ATP]/[ADP][P(i)] calculated from the concentrations of lactate, pyruvate, glyceraldehyde phosphate and 3-phosphoglycerate on the assumption that lactate dehydrogenase, glyceraldehyde phosphate dehydrogenase and 3-phosphoglycerate kinase are at near-equilibrium in the liver. This implies that the redox state of the NAD couple in the cytoplasm is linked to, and partially controlled by, the phosphorylation state of the adenine nucleotides. 2. The combined equilibrium constant of the glyceraldehyde 3-phosphate dehydrogenase and 3-phosphoglycerate kinase reactions at 38 degrees C and I0.25, was found to be 5.9x10(-6). 3. The fall of the [NAD(+)]/[NADH] ratio in starvation and other situations is taken to be the consequence of a primary fall of the [ATP]/[ADP][HPO(4) (2-)] ratio.
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PMID:Equilibrium relations between the cytoplasmic adenine nucleotide system and nicotinamide-adenine nucleotide system in rat liver. 431 32

1. The activities of four enzymes of glycolysis were assayed in the liver of five different strains of rats (four ;Wistar-derived', one Sprague-Dawley) kept on three different but very similar diets. 2. Major strain differences were found for the activities of pyruvate kinase (3-fold), alpha-glycerophosphate dehydrogenase (5-fold), glyceraldehyde phosphate dehydrogenase (3-fold) and triokinase (1.5-fold). 3. Although the initial activities of pyruvate kinase differed greatly the percentage responses to starvation or a diet high in soluble carbohydrate were of the same order in two strains. 4. The importance of considering strain differences is emphasized when making comparisons of measurements carried out in different laboratories.
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PMID:Strain differences in the activities of rat liver enzymes. 534 4

Lysosomal uptake and degradation of polypeptides such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ribonuclease A (RNase A), and RNase S-peptide (residues 1-20 of RNase A) are progressively activated in rat liver by starvation before isolation of lysosomes. This pathway of proteolysis is selective, since it is stimulated by the heat shock cognate protein of 73 kDa (HSC73) and ATP-MgCl2, and lysosomal uptake of RNase A could be competed by GAPDH but not by ovalbumin. A portion of intracellular HSC73 is associated with certain lysosomes, and the amount of lysosomal HSC73 increases by 5- to 10-fold during prolonged starvation. The lysosome-associated HSC73 is primarily within the lysosomal lumen. Double immunogold labeling of lysosomes incubated in vitro with RNase A detects this protein substrate as well as HSC73 within lysosomes. More than two-thirds of the labeled lysosomes contain both RNase A and HSC73. The possible physiological significance of the activation of this selective pathway of lysosomal proteolysis in long-term starvation is discussed.
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PMID:Activation of a selective pathway of lysosomal proteolysis in rat liver by prolonged starvation. 749 10

The secretion pathway of Saccharomyces cerevisiae was challenged by constitutively overexpressing plasmid-encoded acid phosphatase, a secreted endogenous glycoprotein. A 2-microns-based multicopy plasmid carrying the coding sequence of acid phosphatase under the control of a truncated variant of the strong constitutive glyceraldehyde-3-phosphate dehydrogenase promoter was used for expression. Selection for the promoterless dLEU2 marker leads to a growth arrest. This is not per se due to leucine starvation, but due to intracellular accumulation of highly glycosylated enzymatically active acid phosphatase. Immunofluorescence and cytological analysis indicate that intracellular accumulation of acid phosphatase occurs in a subpopulation of cells. By Ludox-AM density centrifugation, these cells can be enriched on the basis of their higher density. The dense accumulating cells have a higher average plasmid copy number and produce more acid phosphatase than non-accumulating cells of low density. These cells are defective in directed secretion and bud formation, therefore can no longer grow and show dramatic changes in cell morphology. We suggest that the secretion pathway in these cells is overloaded with the high level of acid phosphatase leading to a shutdown in vectorial secretion, subsequently to a standstill in growth and to the intracellular accumulation of further expressed acid phosphatase. We have indications that accumulation of acid phosphatase occurs in the late Golgi, suggesting a limitation of the overall secretion at this stage.
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PMID:High-level expression of endogenous acid phosphatase inhibits growth and vectorial secretion in Saccharomyces cerevisiae. 775 60

Three unlinked genes, TDH1, TDH2 and TDH3, encode the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (triose-phosphate dehydrogenase; TDH) in the yeast Saccharomyces cerevisiae. We demonstrate that the synthesis of the three encoded TDH polypeptides (TDHa, TDHb and TDHc, respectively) is not co-ordinately regulated and that TDHa is only synthesised as cells enter stationary phase, due to glucose starvation, or in heat-shocked cells. Furthermore, the synthesis of TDHb, but not TDHc, is strongly repressed by a heat shock. Hence, the TDHa enzyme may play a cellular role, distinct from glycolysis, that is required by stressed cells.
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PMID:Differential synthesis of glyceraldehyde-3-phosphate dehydrogenase polypeptides in stressed yeast cells. 787 59

Oral vanadate administration has been demonstrated to normalize blood glucose levels in ob/ob and db/db mice and streptozotocin (STZ) diabetic rats. The exact mechanism of this vanadate effect is uncertain, since there are no consistent effects on the insulin receptor tyrosine kinase activity or phosphotyrosine phosphatase activity. We have therefore studied the postreceptor actions of vanadate, focusing our attention on the steady-state levels of mRNA of enzymes involved in carbohydrate metabolism. When compared with their lean (ob/+) controls, the livers of ob/ob mice exhibited an approximately 90% reduction in the levels of phosphoenolpyruvate carboxykinase (PEPCK) mRNA and twofold to fivefold higher levels of the mRNAs for glyceraldehyde-3-phosphate dehydrogenase (GAPDH), the "liver beta-cell" glucose transporter (GLUT2), and the proto-oncogene c-myc. Administration of sodium vanadate (0.25 mg/mL) in the drinking water of ob/ob mice over a 45-day period resulted in a near normalization of blood glucose and increased PEPCK mRNA levels more than ninefold. Starvation of the ob/ob mice for 24 to 48 hours also increased PEPCK mRNA levels by fourfold to 15-fold. Vanadate treatment did not alter mRNA levels of any other proteins studied and had no effect on PEPCK mRNA in ob/+ mice. However, 1 to 100 mumol/L vanadate produced a concentration-dependent increase in PEPCK mRNA levels in an H35 hepatoma cell line, an effect opposite to the suppression of PEPCK mRNA produced by insulin. In summary, hyperglycemia in the ob/ob mouse is characterized by decreased expression of PEPCK and increased expression of GAPDH mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Vanadate normalizes hyperglycemia and phosphoenolpyruvate carboxykinase mRNA levels in ob/ob mice. 796 88

Escherichia coli D-glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is produced by the gapA gene and is structurally related to eukaryotic GAPDHs. These facts led to the proposal that the gapA gene originated by a horizontal transfer of genetic information. The yields and start sites of gapA mRNAs produced in various fermentation conditions and genetic contexts were analyzed by primer extension. The transcriptional regulatory region of the gapA gene was found to contain four promoter sequences, three recognized by the vegetative RNA polymerase E sigma 70 and one recognized by the heat shock RNA polymerase E sigma 32. Transcription of gapA by E sigma 32 is activated in the logarithmic phase under conditions of starvation and of heat shock. Using a GAPDH- strain, we found that GAPDH production has a positive effect on cell growth at 43 degrees C. Thus, E. coli GAPDH displays some features of heat shock proteins. One of the gapA promoter sequences transcribed by E sigma 70 is subject to catabolic repression. Another one has growth phase-dependent efficiency. This complex area of differentially regulated promoters allows the production of large amounts of gapA transcripts in a wide variety of environmental conditions. On the basis of these data, the present view of E sigma 32 RNA polymerase function has to be enlarged, and the various hypotheses on E. coli gapA gene origin have to be reexamined.
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PMID:The Escherichia coli gapA gene is transcribed by the vegetative RNA polymerase holoenzyme E sigma 70 and by the heat shock RNA polymerase E sigma 32. 830 May 36


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