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)

Glutamine phosphoribosylpyrophosphate amidotransferase (ATase) activity is rapidly inactivated in stationary-phase cells of Bacillus subtilis. The inactivation of APase requires both the cessation of rapid cell growth and the presence of oxygen. ATase is inactivated in two protease-deficient mutant strains at a rate similar to that seen in the wild type, and is stable in anaerobic cell-free extracts of the parent strain. These results suggest that the inactivation of ATase is not the result of general proteolysis. The inactivation of ATase in stationary-phase cultures can be inhibited by oxygen starvation. This oxygen requirement does not reflect a dependence on the generation of metabolic energy, but appears to be a direct requirement for molecular oxygen. ATase synthesis is repressed by the addition of adenosine, and is inactivated only after the cessation of exponential growth. Addition of chloramphenicol or rifampin to exponential- and stationary-phase cells does not inhibit ATase inactivation, suggesting that protein or ribonucleic acid synthesis is not required for inactivation. ATase is inactivated at the end of exponential growth in cells that have exhausted a required amino acid.
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PMID:Oxygen-dependent inactivation of glutamine phosphoribosylpyrophosphate amidotransferase in stationary-phase cultures of Bacillus subtilis. 80 45

Rates of de novo and salvage purine synthesis decrease by approximately 80 and 60%, respectively, when normal human lymphoblasts are starved 3 h for an essential amino acid (Boss, G. R., and Erbe, R. W. (1982) J. Biol. Chem. 257, 4242-4247). Amino acid starvation decreased the intracellular phosphoribosylpyrophosphate (PP-Rib-P) and ribose 5-phosphate concentrations by approximately 40%, but neither the specific activities of PP-Rib-P synthetase and glutamine amidophosphoribosyltransferase nor the intracellular concentrations of purine nucleotides and inorganic phosphate changed significantly. In mutant cells with either an increased capacity to generate PP-Rib-P (superactive PP-Rib-P synthetase), or an increased PP-Rib-P concentration (inosinate-guanylate:pyrophosphate phosphoribosyltransferase deficiency), the intracellular PP-Rib-P concentration decreased by less than 15% during amino acid starvation and de novo purine synthesis decreased significantly less than in normal cells. When normal cells were treated with drugs that simultaneously decreased feed-back inhibition by purine nucleotides and increased the intracellular concentration of ribose 5-phosphate and PP-Rib-P rates of de novo purine synthesis were stimulated 3-fold in nonstarved cells and more than 8-fold in starved cells. This greater stimulation in the starved cells appeared to be from the increased PP-Rib-P production; moreover, in starved cells in which the increase of the PP-Rib-P concentration by the drugs was impaired because of purine nucleoside phosphorylase deficiency, rates of de novo purine synthesis increased only 3.5-fold. The data suggest that amino acid starvation decreases purine synthesis by decreasing the generation of PP-Rib-P from glucose.
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PMID:Decreased phosphoribosylpyrophosphate as the basis for decreased purine synthesis during amino acid starvation of human lymphoblasts. 619 53

Glutamine phosphoribosylpyrophosphate amidotransferase is stable in growing cells, but is inactivated in an oxygen-dependent process at various rates in starving or antibiotic-treated cells. On the basis of studies of the purified enzyme, we suggested (D.A. Bernlohr and R.L. Switzer, Biochemistry 20:5675-5681, 1981) that the inactivation in vivo was regulated by substrate stabilization and a competition between stabilizing (AMP) and destabilizing (GMP, GDP, and ADP) nucleotides. This proposal was tested by measuring the intracellular levels of these metabolites under cultural conditions in which the stability of the amidotransferase varied. The results established that the stability of amidotransferase in vivo cannot be explained by the simple interactions observed in vitro. Metabolite levels associated with stability of the enzyme in growing cells did not confer stability under other conditions, such as ammonia starvation or refeeding of glucose-starved cells. The data suggest that a previously unrecognized event, possibly a covalent modification of amidotransferase, is required to mark the enzyme for oxygen-dependent inactivation.
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PMID:Regulation of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase inactivation in vivo. 640 10

Glutamine phosphoribosylpyrophosphate amidotransferase, the first enzyme of purine nucleotide biosynthesis, is inactivated and degraded in Bacillus subtilis during carbon, nitrogen, or amino acid starvation. Amidotransferase is stable in exponentially growing cells, and synthesis of the enzyme ceases prior to its inactivation at the end of exponential growth. Inactivation has been previously shown to result from reaction of an essential [4Fe-4S] center with oxygen. In this work, monospecific antibodies against amidotransferase have been used to demonstrate that inactivation is followed by proteolytic degradation in vivo and that the metabolic requirements for degradation differ from those for inactivation. Unlike inactivation, degradation is inhibited by addition of 10 mM KCN or antibiotic inhibitors of RNA and protein synthesis to glucose-starved cells. The cross-reactive material that accumulates when degradation is inhibited by chloramphenicol initially has native subunit molecular weight, but lower molecular weight polypeptides slowly accumulate. Degradation, but not inactivation, of amidotransferase is strongly inhibited during amino acid starvation of a relA strain. Degradation of amidotransferase is inhibited by pseudomonic acid, an antibiotic that blocks protein synthesis but permits a normal stringent response. This result indicates that both protein synthesis and normal relA gene function are required for degradation.
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PMID:Degradation of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase in vivo. 640 5

1. Urate synthesis was measured in hepatocytes from chickens after starvation or high-protein feeding. Adaptation occurred only on the high-protein diet. 2. The theoretical balances of reactions from alanine (5 alanine + 3 O2 = urate + 1.5 glucose + glycine) and asparagine (3 asparagine + 2 O2 = urate + ammonia + 0.5 glucose + glycine) agree reasonably well with the experimental results. 3. Enzymes directly involved in urate synthesis from these amino acids increase up to 12-fold on the high-protein diet; only amidophosphoribosyltransferase activity appears to be rate-limiting for urate synthesis. 4. The processes of nitrogen disposal in chicken and rat are compared and discussed.
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PMID:Adaptation of urate synthesis in chicken liver. 712 10

Two structurally similar but functionally distinct PII-like proteins, PII and GlnK, regulate nitrogen assimilation in Escherichia coli. Studies with cells indicated that both PII (the glnB product) and GlnK (the glnK product) acted through the kinase/phosphatase NRII [NtrB, the glnL (ntrB) product] to reduce transcription initiation from Ntr promoters, apparently by regulating the phosphorylation state of the transcriptional activator NRI-P (NtrC-P, the phosphorylated form of the glnG (ntrC) product). Both GlnK and PII also acted through adenylyltransferase (ATase, the glnE product) to regulate the adenylylation state of glutamine synthetase (GS). The activity of both GlnK and PII was regulated by the signal-transducing uridylyltransferase/uridylyl-removing enzyme (UTase/UR, glnD product). Our experiments indicate that either PII or GlnK could effectively regulate ATase, but that PII was required for the efficient regulation of NRII required to prevent expression of glnA, which encodes GS. Yet, GlnK also participated in regulation of NRII. Although cells that lack either PII or GlnK grew well, cells lacking both of these proteins were defective for growth on nitrogen-rich minimal media. This defect was alleviated by the loss of NRII, and was apparently due to unregulated expression of the Ntr regulon. Also, mutations in glnK, designated glnK*, were obtained as suppressors of the Ntr- phenotype of a double mutant lacking PII and the UTase/UR. These suppressors appeared to reduce, but not eliminate, the ability of GlnK to prevent Ntr gene expression by acting through NRII. We hypothesize that one role of GlnK is to regulate the expression of the level of NRI-P during conditions of severe nitrogen starvation, and by so doing to contribute to the regulation of certain Ntr genes.
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PMID:Role of the GlnK signal transduction protein in the regulation of nitrogen assimilation in Escherichia coli. 972 Aug 63

The prevalence of paralogous enzymes implies that novel catalytic functions can evolve on preexisting protein scaffolds. The weak secondary activities of proteins, which reflect catalytic promiscuity and substrate ambiguity, are plausible starting points for this evolutionary process. In this study, we observed the emergence of a new enzyme from the ASKA (A Complete Set of E. coli K-12 ORF Archive) collection of Escherichia coli open reading frames. The overexpression of (His)(6)-tagged glutamine phosphoribosylpyrophosphate amidotransferase (PurF) unexpectedly rescued a Delta trpF E. coli strain from starvation on minimal media. The wild-type PurF and TrpF enzymes are unrelated in sequence, tertiary structure and catalytic mechanism. The promiscuous phosphoribosylanthranilate isomerase activity of the ASKA PurF variant apparently stems from a preexisting affinity for phosphoribosylated substrates. The relative fitness of the (His)(6)-PurF/Delta trpF strain was improved 4.8-fold to nearly wild-type levels by random mutagenesis of purF and genetic selection. The evolved and ancestral PurF proteins were purified and reacted with phosphoribosylanthranilate in vitro. The best evolvant (k(cat)/K(M)=0.3 s(-1) M(-1)) was approximately 25-fold more efficient than its ancestor but >10(7)-fold less efficient than the wild-type phosphoribosylanthranilate isomerase. These observations demonstrate in quantitative terms that the weak secondary activities of promiscuous enzymes can dramatically improve the fitness of contemporary organisms.
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PMID:A study in molecular contingency: glutamine phosphoribosylpyrophosphate amidotransferase is a promiscuous and evolvable phosphoribosylanthranilate isomerase. 1827 77