The Effects of Bases and Nucleosides on the Intracellular Contents of Nucleotides and 5‐Phosphoribosyl 1‐pyrophosphate in <i>Escherichia coli</i>

Bagnara, Aldo S.; Finch, Lloyd R.

doi:10.1111/j.1432-1033.1974.tb03283.x

Cited by 64 publications

(19 citation statements)

References 21 publications

(13 reference statements)

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“…1) were inhibited 60 to 70% by UMP, while ornithine stimulated activities 100 to 300%. These characteristics are comparable to the regulatory controls observed for E. coli (1,4). Similarly, there were no apparent differences between the various ornithine transcarbamoylases and their E. coli counterpart.…”

supporting

confidence: 66%

ATP-liganded form of aspartate transcarbamoylase, the logical regulatory target for allosteric control in divergent bacterial systems

1988

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In Escherichia coli, the mechanism for regulatory control of aspartate transcarbamoylase is clear; CTP allosterically inhibits catalysis in direct competition with ATP. However, both CTP and ATP may be activators or may have no effect on aspartate transcarbamoylases from other enteric bacteria. A common regulatory logic observed was that the ATP-activated enzymes were rendered less active as the result of competition with CTP, regardless of the independent effects.

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supporting

confidence: 66%

ATP-liganded form of aspartate transcarbamoylase, the logical regulatory target for allosteric control in divergent bacterial systems

1988

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“…However, in the presence of adenine (100 mg/liter) this strain became NAD auxotrophic. Adenine is a potent scavenger of PRPP in cells that contain a wild-type allele of the apt gene, which encodes adenine phosphoribosyltransferase (2). In addition, the strain formed colonies in the absence of tryptophan, although at a much lower rate than it formed colonies in the absence of NAD.…”

Section: Methodsmentioning

confidence: 99%

Escherichia coli phnN , Encoding Ribose 1,5-Bisphosphokinase Activity (Phosphoribosyl Diphosphate Forming): Dual Role in Phosphonate Degradation and NAD Biosynthesis Pathways

et al. 2003

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An enzymatic pathway for synthesis of 5-phospho-D-ribosyl ␣-1-diphosphate (PRPP) without the participation of PRPP synthase was analyzed in Escherichia coli. This pathway was revealed by selection for suppression of the NAD requirement of strains with a deletion of the prs gene, the gene encoding PRPP synthase (B. Hove-Jensen, J. Bacteriol. 178:714-722, 1996). The new pathway requires three enzymes: phosphopentomutase, ribose 1-phosphokinase, and ribose 1,5-bisphosphokinase. The latter activity is encoded by phnN; the product of this gene is required for phosphonate degradation, but its enzymatic activity has not been determined previously. The reaction sequence is ribose 5-phosphate 3 ribose 1-phosphate 3 ribose 1,5-bisphosphate 3 PRPP. Alternatively, the synthesis of ribose 1-phosphate in the first step, catalyzed by phosphopentomutase, can proceed via phosphorolysis of a nucleoside, as follows: guanosine ؉ P i 3 guanine ؉ ribose 1-phosphate. The ribose 1,5-bisphosphokinase-catalyzed phosphorylation of ribose 1,5-bisphosphate is a novel reaction and represents the first assignment of a specific chemical reaction to a polypeptide required for cleavage of a carbon-phosphorus (COP) bond by a C-P lyase. The phnN gene was manipulated in vitro to encode a variant of ribose 1,5-bisphosphokinase with a tail consisting of six histidine residues at the carboxy-terminal end. PhnN was purified almost to homogeneity and characterized. The enzyme accepted ATP but not GTP as a phosphoryl donor, and it used ribose 1,5-bisphosphate but not ribose, ribose 1-phosphate, or ribose 5-phosphate as a phosphoryl acceptor. The identity of the reaction product as PRPP was confirmed by coupling the ribose 1,5-bisphosphokinase activity to the activity of xanthine phosphoribosyltransferase in the presence of xanthine, which resulted in the formation of 5-XMP, and by cochromatography of the reaction product with authentic PRPP.NAD biosynthesis in Escherichia coli usually proceeds by consumption of 5-phospho-D-ribosyl ␣-1-diphosphate (PRPP). NAD is synthesized from aspartate and dihydroxyacetone phosphate. A de novo pathway and a number of salvage pathways for the reutilization of nicotinamide mononucleotide and nicotinamide exist, as shown in Fig. 1 (32). Two of the enzymatic reactions, the reactions catalyzed by quinolinate and nicotinate phosphoribosyltransferases, require PRPP. PRPPless mutants with a deletion of the prs gene, encoding PRPP synthase, consequently require NAD or nicotinamide mononucleotide. ⌬prs strains also require guanosine, uridine, histidine, and tryptophan, which are likewise synthesized with PRPP as an intermediate (14,15). Nevertheless, mutants that suppress the NAD requirement are easily obtained by selecting for growth of ⌬prs cells on medium lacking NAD. These mutants still require guanosine, uridine, histidine, and tryptophan. All such NAD-suppressed mutants were previously shown to have lesions in the pst-phoU operon (17), which leads to highlevel constitutive expression of genes belonging to the phosphate (Ph...

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“…The biochemical parameters of the mutant enzyme were inconsistent with the initial model suggested by the in vivo phenotype, which predicted an increased K m for FGAM. Exogenous purines have been reported to increase ATP levels slightly, which if anything might be expected to increase the activity of the mutant protein (2). However, in vivo the mutant protein appeared to be inhibited, either directly or indirectly, by exogenous purines.…”

Section: Vol 183 2001mentioning

confidence: 89%

“…There are three known levels of regulation on this pathway: (i) transcription of pur genes is repressed by PurR (with its corepressors hypoxanthine and guanine) (17,18,22,28,33,39), (ii) allosteric inhibition of the first committed step in purine biosynthesis (phosphoribosylpyrophosphate amidotransferase, PurF) by AMP and GMP (24), and (iii) control of the levels of phosphoribosylpyrophosphate (PRPP), a substrate for the PurF enzyme. The level of PRPP in the cell drops substantially in the presence of exogenous purines (2,19). Labeling studies suggest that exogenous adenine reduces flux through the purine biosynthetic pathway to 10% of that on minimal medium (32).…”

mentioning

confidence: 99%

Altered Pathway Routing in a Class of Salmonella enterica Serovar Typhimurium Mutants Defective in Aminoimidazole Ribonucleotide Synthetase

et al. 2001

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In Salmonella enterica serovar Typhimurium, purine nucleotides and thiamine are synthesized by a branched pathway. The last known common intermediate, aminoimidazole ribonucleotide (AIR), is formed from formylglycinamidine ribonucleotide (FGAM) and ATP by AIR synthetase, encoded by the purI gene in S. enterica. Reduced flux through the first five steps of de novo purine synthesis results in a requirement for purines but not necessarily thiamine. To examine the relationship between the purine and thiamine biosynthetic pathways, purI mutants were made (J. L. Zilles and D. M. Downs, Genetics 143:37-44, 1996). Unexpectedly, some mutant purI alleles (R35C/E57G and K31N/A50G/L218R) allowed growth on minimal medium but resulted in thiamine auxotrophy when exogenous purines were supplied. To explain the biochemical basis for this phenotype, the R35C/E57G mutant PurI protein was purified and characterized kinetically. The K m of the mutant enzyme for FGAM was unchanged relative to the wild-type enzyme, but the V max was decreased 2.5-fold. The K m for ATP of the mutant enzyme was 13-fold increased. Genetic analysis determined that reduced flux through the purine pathway prevented PurI activity in the mutant strain, and purR null mutations suppressed this defect. The data are consistent with the hypothesis that an increased FGAM concentration has the ability to compensate for the lower affinity of the mutant PurI protein for ATP.In Salmonella enterica serovar Typhimurium LT2, purines and thiamine are synthesized via a divergent pathway where 5-aminoimidazole ribonucleotide (AIR) is the intermediate at the branch point (Fig. 1). Since the cellular purine requirement is approximately 10 3 -fold higher than the thiamine requirement (based on auxotrophic requirements), this pathway provides a model to address control of an important metabolic branch point. Previous genetic and molecular analyses demonstrated that even 1% of the wild-type level of AIR synthetase was sufficient to supply the cellular requirement for thiamine but not purines (J. L. Zilles and D. M. Downs, submitted for publication), indicating that thiamine synthesis can be maintained even when flux through the common pathway is severely reduced. Under this condition, thiamine synthesis could continue if levels of the substrate (presumed to be AIR) remained above the K m for the first committed thiamine enzyme or if there were metabolite channeling between PurI and the thiamine enzyme (thought to be ThiC). Mutational analysis of purI, encoding the final common enzyme AIR synthetase, was pursued to clarify the parameters controlling thiamine synthesis with changing flux through the purine pathway.The synthesis of AIR, via the pathway common to purine and thiamine synthesis, appears to be regulated only in response to exogenous purines. There are three known levels of regulation on this pathway: (i) transcription of pur genes is repressed by PurR (with its corepressors hypoxanthine and guanine) (17,18,22,28,33,39), (ii) allosteric inhibition of the first committed...

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The Effects of Bases and Nucleosides on the Intracellular Contents of Nucleotides and 5‐Phosphoribosyl 1‐pyrophosphate in Escherichia coli

Cited by 64 publications

References 21 publications

ATP-liganded form of aspartate transcarbamoylase, the logical regulatory target for allosteric control in divergent bacterial systems

ATP-liganded form of aspartate transcarbamoylase, the logical regulatory target for allosteric control in divergent bacterial systems

Escherichia coli phnN , Encoding Ribose 1,5-Bisphosphokinase Activity (Phosphoribosyl Diphosphate Forming): Dual Role in Phosphonate Degradation and NAD Biosynthesis Pathways

Altered Pathway Routing in a Class of Salmonella enterica Serovar Typhimurium Mutants Defective in Aminoimidazole Ribonucleotide Synthetase

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