Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The heterogeneity of undermodified phenylalanine tRNA produced in relaxed control E. coli during amino acid starvation was investigated. Examination of the RPC-5 elution profiles of tRNAPhe prepared from non-starved cells and cells starved of a variety of amino acids, including some known to be involved in the formation of modified bases revealed that: (1) only one species of fully modified tRNAPhe appears to occur in cells grown in enriched medium; (2) at least two chromatographically unique isoacceptor species are observed in addition to the normal tRNAPhe in starved cells; (3) the unique, undermodified species of tRNAPhe from leucine-starved cells, known to be deficient in dihydrouridine, pseudouridine, 2-thiomethyl-N6-(delta2-isopentenyl) adenosine and 3-(3-amino-3-carboxypropyl) uridine, co-elute with the unique species produced in cells starved of histidine or arginine or treated with puromycin or chloramphenicol; (4) additional unique species of tRNAPhe can be detected in methyl- and sulfur-deficient tRNA from methionine- and cysteine-starved cells; (5) analysis of phenoxyacetylated tRNA revealed that the chromatographically unique and normal species from starved cells contain subspecies deficient in 3-(3-amino-3-carboxypropyl) uridine; and (6) using phenoxyacetylation as a means of effecting the resolution of undermodified subspecies, a total of at least ten chromatographically unique subspecies of rRNAPhe were detected in an organism that appears to posses only one gene for tRNAPhe. Taken together, the results support the view that there are both general and specific effects of amino acid starvation on the post-transcriptional modification of tRNA.
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PMID:General and specific effects of amino acid starvation on the formation of undermodified Escherichia coli phenylalanine tRNA. 79 74

The ATP sulfurylase of cultured tobacco cells is repressed during growth on readily assimiliated sulfur sources, such as sulfate, L-cysteine, or L-methionine, but it is derepressed during growth on slowly assimiliated sulfur sources, such as L-djenkolate or glutathione, or during sulfur starvation. The enzyme is not induced by sulfate. The enzyme level in the cells begins to rise 12 to 24 h after the derepression conditions are initiated and continues to rise for 3 to 4 days, up to as much as 25 times above the initial specific activity. Addition of a repressing sulfur source to derepressed cells causes the enzyme to decay. Derepression by sulfur limitation does not occur in cells starved for nitrogen, a circumstance in which turnover synthesis of protein is known to continue. Upon addition of a nitrogen source to such cells, the development of the enzyme begins within 12 h, along with the resumption of growth and net protein synthesis. Derepression occurs in cells growing on the slowly assimilated nitrogen in urea, reaching specific activities very similar to those which develop in cells grown on nitrate, in spite of the lower protein accumulation rate on urea. Thus the ATP sulfurylase of tobacco cells appears to be regulated by both a negative feedback mechanism in which an end product of the sulfate assimilation pathway is the effector, and by a positive mechanism which serves to couple the regulation of the sulfate assimilation pathway to the cells' potential for nitrogen assimilation, i.e. net protein synthesis. The sulfur compounds which affect the development of ATP sulfurylase in vivo have no effect on the enzyme activity in vitro. Furthermore, extracts with high activity contain no activator and extracts with low activity contain no inhibitor of ATP sulfurylase. Cycloheximide, at a concentration which strongly inhibits amino acid incorporation into protein, inhibits derepression. ATP sulfurylase does not decay in cells inhibited by cycloheximide. Therefore, the changes in ATP sulfurylase of tobacco cells appear to involve changes in the rate of formation or degradation of the enzyme.
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PMID:Regulation of adenosine triphosphate sulfurylase in cultured tobacco cells. Effects of sulfur and nitrogen sources on the formation and decay of the enzyme. 84 48

It has been shown that the net rate of gluconeogenesis from cysteine was only 10% the rate observed from pyruvate. This suggested that the rate limiting step in gluconeogenesis from cysteine was between cysteine and pyruvate. Evidence is presented showing that the cysteine-sulfinate pathway does not play a regulating role in the conversion of cysteine to glucose. Thus, liver cysteine desulfhydrase (CDS) activity and hydrogen sulfide production were evaluated for their potential effects. Liver CDS activity was increased by a 3 day starvation, by feeding a 90% casein diet or a 4% cysteine + 86% casein diet. In all cases the activity of the enzyme was in excess of that required to account for the rate of conversion of cysteine to glucose observed, thus the potential activity of this enzyme was not a rate limiting factor. The possible effect of H2S, an end product of the CDS reaction, on gluconeogenesis from cysteine was evaluated. The addition of NaHS abolished the glucogenic response observed from cysteine, but had very little effect on glucoeogenesis from lactate, suggesting that accumulated H2S may inhibit CDS, marking CDS rate limiting in the conversion of cysteine to pyruvate.
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PMID:Fractors affecting the rate of gluconeogenesis from L-cysteine in the perfused rat liver. 95 11

The inhibition of Salmonella typhimurium by 1,2,4-triazole appears to be mediated through an effect on L-cysteine biosynthesis. O-Acetylserine sulfhydrylase A, the final enzyme in the L-cysteine biosynthetic pathway, was found to catalyze a reaction (triazolylase) between O-acetyl-L-serine and 1,2,4-triazole, giving 1,2,4-triazole-1-alanine as a product. In wild type S. typhimurium grown on 4 mM 1,2,4-triazole, 97% of the total O-acetyl-L-serine synthesized in vivo is incorporated into 1,2,4-triazole-1-alanine. 1,2,4-triazole also significantly lowers the levels of several of the enzymes necessary for sulfate reduction. This effect is presumably due to the ability of the inhibitor to lower intracellular concentrations of O-acetyl-L-serine, an inducer of these enzymes. Inhibition of growth is probably caused by L-cysteine starvation, arising from the decreased availability of the L-cysteine precursors, sulfide and O-acetyl-L-serine. Two 1,2,4-triazole-resistant strains bearing mutations in cysK, the structural gene for O-acetylserine sulfhydrylase A, incorporate only small quantities of O-acetyl-L-serine into 1,2,4-triazole-1-alanine in vivo. In vitro studies, using purified preparations of O-acetylserine sulfhydrylase A, revealed greater losses of triazolylase activity than sulfhydrylase activity in the enzymes from both cysK mutants. Resistance to 1,2,4-triazole apparently can arise from mutations leading to a preferential loss of triazolylase activity or from mutations which diminish both activities to the extent that high concentrations of O-acetyl-L-serine and sulfide accumulate behind the sulfhydrylase reaction.
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PMID:Studies on the mechanism of inhibition of Salmonella typhimurium by 1,2,4-triazole. 110 Jun 24

The effects of dietary treatments and substrate availability on the rate of gluconeogenesis from L-cysteine has been investigated in the perfused rat liver. At an optimal concentration (10 mM) of [U-14C]cysteine, after 40 minutes, 3.9% of the label appeared in glucose. This corresponded to 90% of the net glucose coming from cysteine. Cysteine was then shown to be converted to glucose at a physiological concentration of substrate (0.1 mM) as well as at the optimal concentration. After 40 minutes of perfusion with 0.1 mM [U-14C]cysteine as the substrate, livers of 72-hour starved rats incorporated 1.7% of the label into glucose, and livers of rats perfused without prior starvation incorporated 0.53% of the label into glucose. This suggested that cysteine was glucogenic at optimal and physiological concentrations of cysteine in both fed and starved rats. To determine which, if either, of the two suggested pathways for the conversion of cysteine to glucose was quantitatively more important, livers were perfused with [U-14C]cysteine alone or with [U-14C]cysteine plus cysteine sulfinic acid. The addition of cysteine sulfinate (10 mM) reduced the incorporation of 14C from cysteine into glucose from 3.9 to 2.7%. This suggested that one-third of the cysteine to glucose proceeded via the cysteine sulfinate-dependent pathway.
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PMID:Relative importance of the two major pathways for the conversion of cysteine to glucose in the perfused rat liver. 119 10

We have previously shown that resistance to the beta-lactam mecillinam in Escherichia coli can be brought about by a high ppGpp pool, as observed under conditions of partial amino acid starvation and RelA-dependent induction of the stringent response. We show here that our E. coli wild-type strain, which is sensitive to mecillinam on minimal glucose plates, becomes resistant in the presence of L-leucine or L-serine (or cysteine, which inactivates the antibiotic). The resistance, which is not a transient effect and does not depend on the physiological state of the cells when plated, is specific for mecillinam and is reversed by the presence of isoleucine and valine in the medium. At least in the case of serine, the resistance is RelA-dependent. We conclude that the presence of leucine and serine in the growth medium cause partial starvation for isoleucine/valine, leading to induction of the stringent response and concomitant resistance to mecillinam.
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PMID:Leucine and serine induce mecillinam resistance in Escherichia coli. 146 98

Mevalonate starvation of hamster fibroblasts resulted in a shift of rab1b from the membrane to the cytosolic fraction, suggesting that rab1b depends upon an isoprenoid modification for its membrane localization. rab1b and rab3a proteins expressed in insect cells incorporated a product of [3H]mevalonate, and gas chromatography analysis of material released by Raney nickel cleavage demonstrated that rab1b and rab3a are modified by geranylgeranyl groups. Additionally, in vitro prenylation analysis demonstrated farnesyl modification of H-ras but geranylgeranyl modification of five rab proteins (1a, 1b, 2, 3a, and 6). Together, these results suggest that the carboxyl-terminal CC/CXC motifs (X = any amino acid) specifically signal for addition of geranylgeranyl, but not farnesyl, groups. A rab1b mutant protein lacking the two carboxyl-terminal cysteine residues was not prenylated in vitro. However, since a mutant H-ras protein that terminates with tandem cysteine residues was also not modified, the CC motif may be essential, but not sufficient, to signal prenylation of rab1b. Finally, rab1b and rab3a proteins were not efficient substrates for either farnesyl- or geranylgeranyltransferase activities that modify CAAX-containing proteins (A = any aliphatic amino acid). Therefore, rab proteins may be modified by a prenyltransferase(s) distinct from the prenyltransferases that modify carboxyl-terminal CAAX proteins.
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PMID:Isoprenoid modification of rab proteins terminating in CC or CXC motifs. 164 36

The response to injury and infection can be viewed as a mobilization of body protein, fat, and carbohydrate stores to ensure normal or above-normal circulating levels of substrate in the absence of dietary intake. The situation does not readily yield to nutritional manipulation, and inappropriate nutritional support can cause additional stress. Artificial nutrition is mainly a form of nutrient administration and not nutrient utilization. Modulation of neurohumoral and wound responses to trauma due to starvation and refeeding has not been delineated. The provision of adequate substrates alone does not necessarily guarantee their efficient use in metabolism. With a clear knowledge of the role of cellular mediators in the pathophysiology of disease, it may be possible to develop more rational therapeutic approaches during critical illness. Determination of appropriate and optimal substrate support through parenteral and enteral nutrition remains of great clinical importance. The clinical application of branched-chain amino acids, dispensable amino acids, acetylated amino acids, dipeptides or tripeptides, cysteine, glutamine, and arginine has been explored in recent years. The idea that lipids are deleterious in sepsis and organ failure should be revised and documented, and recent studies suggest that fish oils as a lipid source may also favorably affect immune responses. Under stressful conditions, total parenteral nutrition can require large amounts of energy at a time when there are marked disturbances in glucose utilization. In this area, the use of nonglucose carbohydrates or oligosaccharides can be appropriate, despite the lack of broad acceptance. Existing conventional substrates should be studied beyond mere provision of energy and metabolic pathway support.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nutritional and metabolic support: converging concepts. 180 4

Cysteine, in concentrations down to 0.04 micrograms/ml, induces transient amino acid starvation in Escherichia coli growing in minimal medium. The duration depends on the concentration and is 5 min at 2 micrograms of cysteine per ml. At low cysteine concentrations, threonine and isoleucine almost completely abolish the starvation.
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PMID:Cysteine, even in low concentrations, induces transient amino acid starvation in Escherichia coli. 190 68

Hypertrehalosemic hormone (a carbohydrate-mobilizing neuroendocrine decapeptide) and starvation markedly increased levels of a cockroach (Blaberus discoidalis) fat body cytochrome P450 message. The gene represented by the cloned P450 cDNA has been named CYP4C1 (cytochrome P450 family 4, subfamily C, gene 1), a newly identified member of the ubiquitous cytochrome P450 monooxygenase gene superfamily. Blaberus CYP4C1 (511 amino acids, Mr = 58,485) has a hydrophobic NH2 terminus and a sequence near the COOH terminus that is homologous to the cysteine-containing heme-binding region definitive of cytochromes P450. The cockroach sequence is 32-36% identical to mammalian family 4A and 4B enzymes. It contains a 13-residue sequence characteristic of family 4 but not other P450s. This study suggests that CYP4C1 is hormonally regulated in association with energy substrate mobilization and supports the idea that family 4 is an old and widespread gene family.
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PMID:Cytochrome P450 family 4 in a cockroach: molecular cloning and regulation by regulation by hypertrehalosemic hormone. 203 94


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