Regulation of Salmonella phosphoribosylpyrophosphate synthetase activity in vivo. Deductions from pool measurements

Sadler, William; Switzer, Robert L.

doi:10.1016/s0021-9258(19)75248-x

Cited by 28 publications

(2 citation statements)

References 32 publications

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“…The AMP concentration may also rise under these conditions, but the net effect would be destabilization of amidotransferase (e.g" in the presence of 1.0 mM each of AMP, ADP, GMP, and GDP, the half-life of the enzyme is 15 min; this is equivalent to a half-life under air of about 75 min, which is close to the half-life observed in vivo). As a first approximation, we suggest that the effects of P-Rib-PP concentration are secondary, because the P-Rib-PP concentration probably never exceeds 400 µ (Sadler & Switzer, 1977). Obviously, the validity of this model is unproven.…”

Section: Discussionmentioning

confidence: 83%

Reaction of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase with oxygen: chemistry and regulation by ligands

Bernlohr¹,

Switzer²

1981

Biochemistry

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The inactivation of glutamine phosphoribosylpyrophosphate amidotransferase by reaction of its iron-sulfur center with O2 is believed to be a physiologically important mode of regulation of this enzyme in Bacillus subtilis cells in the stationary phase of growth. Chemical and physical changes accompanying oxidation of the purified enzyme by O2 were studied. The iron of the 4Fe-4S center was oxidized to enzyme-bound high-spin Fe3+; the S2- was oxidized to a mixture of S0 bound as thiocystine and unidentified products. The oxidant appeared to be O2, rather than peroxide, superoxide, hydroxyl radical, or singlet oxygen. Gross physical changes in the oxidized enzyme were shown by its aggregation, decreased solubility, and altered circular dichroic spectrum. Experimental variables affecting the rate of oxidative inactivation were described; the most important of these was modulation of rates of inactivation by the allosteric inhibitors AMP, ADP, GMP, GDP and by the substrate P-Rib-PP. AMP was a potent stabilizer, whose effect was antagonized by P-Rib-PP. The other nucleotides, either acting singly or acting as synergistic pairs, were destabilizers and able to antagonize stabilization by AMP. The results are discussed in terms of the regulation of the stability of amidotransferase and its degradation in vivo.

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Section: Discussionmentioning

confidence: 83%

Reaction of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase with oxygen: chemistry and regulation by ligands

Bernlohr¹,

Switzer²

1981

Biochemistry

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“…The value of K m PRPP determined for the L. lactis enzyme (18.4 ( 3.5 µM) is similar to the values determined for the hexameric prokaryotic enzymes but lower than the values for the two isoforms of A. thaliana (Table 1). Notably, the Michaelis constants for PRPP for the two ATP-PRT classes in prokaryotic enzymes are significantly lower than the estimated intracellular concentration of PRPP in S. typhimurium, which has been measured to be 350 µΜ (30). Under typical physiological conditions, therefore, the hexameric and heterooctameric forms of the enzyme would both be expected to be saturated with PRPP, providing little regulation by this substrate.…”

Section: Discussionmentioning

confidence: 86%

Substrate Recognition by the Hetero-Octameric ATP Phosphoribosyltransferase from Lactococcus lactis

2006

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Two families of ATP phosphoribosyl transferases (ATP-PRT) join ATP and 5-phosphoribosyl-1 pyrophosphate (PRPP) in the first reaction of histidine biosynthesis. These consist of a homohexameric form found in all three kingdoms, and a hetero-octameric form largely restricted to bacteria. Hetero-octameric ATP-PRTs consist of four HisG S catalytic subunits related to periplasmic binding proteins, and four HisZ regulatory subunits that resemble histidyl-tRNA synthetases. To clarify the relationship between the two families of ATP-PRTs, and among phosphoribosyltransferases in general, we determined the steady state kinetics for the heterooctameric form, and characterized the active site by mutagenesis. The K m PRPP (18.4 ± 3.5 μM) and k cat (2.7 ± 0.3 sec −1 ) values for the PRPP substrate are similar to those of hexameric ATP-PRTs, but the K m for ATP (2.7 ± 0.3 mM) is 4-fold higher, suggestive of tighter regulation by energy charge. Histidine and AMP were determined to be non-competitive (K i = 81.1 μM) and competitive (K i = 1.44 mM) inhibitors, respectively, with values that approximate their intracellular concentrations. Mutagenesis experiments investigating the side chains recognizing PRPP showed that 5′ phosphate contacts (T159A and T162A) had the largest (25-and 155-fold) decreases in k cat /K m , while smaller decreases were seen with mutants making cross subunit contacts (K50A and K8A) to the pyrophosphate moiety, or contacts to the 2′ OH. Despite their markedly different quaternary structures, hexameric and hetero-octameric ATRP-PRTs exhibit similar functional parameters, and employ mechanistic strategies reminiscent of the broader PRT superfamily.ATP phosphoribosyltransferase (ATP-PRT; E. C. 2.4.2.17) catalyzes the first and highly regulated step of histidine biosynthesis, which involves nucleophillic attack of the N1 of ATP on C1′ of 5-phosphoribosyl-1 pyrophosphate (PRPP) to form N-1-(5′-phosphoribosyl)-ATP (PR-ATP, Figure 1A) (1). The resulting product is converted through an additional nine reactions into histidine by a pathway that is regulated both by its end product and by AMP and ADP (2). The tight regulation of this pathway (reviewed in (3)), reflects the high energetic costs associated with histidine synthesis, and the need to dramatically slow pathway flux when histidine is present in the growth media (4). Superimposed on top of metabolic control of † This work was supported by N.I.H. grant GM54899 (CSF) histidine biosynthesis is genetic regulation of the expression of histidine biosynthetic enzymes, by use of the classic attenuation mechanism (reviewed in (5)).ATP-PRT is a member of the phophoribosyltransferase (PRT) superfamily of enzymes, all of whom share a common chemistry that involves transfer of the phosphoribosyl group to a nucleotide base or, in the case of glutamine phosphoribosyl pyrophosphate amidotransferase, to free ammonia generated on the enzyme (6). PRTs are found in many essential pathways, including biosynthesis and salvage of nucleotides, and the synthesis of cofac...

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Yeast sequencing reports. Isolation of phosphoribosylpyrophosphate synthetase (PRS1) gene from Candida albicans

Payne

Calderone

1995

Yeast

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We have isolated a 3.7 kb EcoR1 fragment from a genomic library of Candida albicans which displayed a 65% level of identity with the PRS gene family (PRS) of Saccharomyces cerevisiae. The PRS gene encodes a phosphoribosylpyrophosphate (PRPP) synthetase of S. cerevisiae, which catalyses the synthesis of purines, pyrimidines, and amino acids such as histidine and tryptophan. By Northern analyses, we observed that the entire 3.7 kb EcoR1 fragment as well as 1.1 kb KpnI-SacI internal fragment of the 3.7 kb EcoR1 fragment hybridized to the same 1.4 kb transcript. An internal 2.6 kb KpnI fragment was subcloned and sequenced. A deduced sequence of 321 amino acids representing a polypeptide of 35.2 kDa was determined. A FASTA search indicated that the C. albicans PRS (Ca PRS1) had an overall homology at the amino acid level of 91% with the S. cerevisiae PRS3. Putative transcriptional start and termination sequences as well as a cation-binding, PRPP synthetase signature sequence were identified. Ca PRS1 was localized to chromosome 2 of the C. albicans genome. Low stringency hybridizations indicates that the organism may possess multiple PRS genes. The function of these genes in nitrogen signaling is discussed.

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Regulation of Salmonella phosphoribosylpyrophosphate synthetase activity in vivo. Deductions from pool measurements

Cited by 28 publications

References 32 publications

Reaction of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase with oxygen: chemistry and regulation by ligands

Reaction of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase with oxygen: chemistry and regulation by ligands

Substrate Recognition by the Hetero-Octameric ATP Phosphoribosyltransferase from Lactococcus lactis

Yeast sequencing reports. Isolation of phosphoribosylpyrophosphate synthetase (PRS1) gene from Candida albicans

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