862. The simple fluorides of iridium, including the new trifluoride

Robinson, Percy Lucock; Westland, G. J.

doi:10.1039/jr9560004481

Cited by 25 publications

(12 citation statements)

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“…Partially hydrolyzed polyP 750 was fractionated by 6% ureapolyacrylamide gel and then eluted from gel slices into 50 mM ammonium acetate, followed by ethanol precipitation (4).…”

Section: Methodsmentioning

confidence: 99%

“…Such enzymes have been identified in a variety of microorganisms. PolyP kinase, the enzyme that catalyzes the reversible transfer of the terminal phosphate from ATP to synthesize polyP, has been purified to homogeneity in several bacteria (3)(4)(5). Exopolyphosphatases that catalyze the hydrolysis of terminal phosphates from polyP have been purified from Escherichia coli (6), Corynebacterium xerosis (7), and Saccharomyces cerevisiae (8,9).…”

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confidence: 99%

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Endopolyphosphatases for Long Chain Inorganic Polyphosphate in Yeast and Mammals

Kumble

Kornberg

1996

Journal of Biological Chemistry

122

108

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Whereas exopolyphosphatases have been purified from yeast and a variety of bacteria, this is the first report characterizing endopolyphosphatases that act on long chain inorganic polyphosphate (polyP). The activity from Saccharomyces cerevisiae, localized in vacuoles, has been purified to homogeneity from a strain that possesses vacuolar proteases. The endopolyphosphatase is a dimer of 35-kDa subunits. Distributive action on polyP 750 produces shorter chains to a limit of about polyP 60 , as well as the more abundant release of polyP 3 ; the K m for polyP 750 is 185 nM. Endopolyphosphatases have been identified in a wide variety of sources, except for most eubacteria tested. The activity has been partially purified from rat and bovine brain where its abundance is about 10 times higher than in other tissues but less than 1 ⁄10 that of yeast; the limit product of digestion of the partially purified brain enzyme is polyP 3 .Inorganic polyphosphates (polyP) 1 are linear polymers of orthophosphate residues linked by high energy phosphoanhydride bonds. Likely prevalent in prebiotic evolution (1) polyP has been found in all organisms ranging from bacteria to mammals (2). The ubiquitous occurrence of polyP suggests multiple roles depending on the species, cell, subcellular localization, and physiological state.Our approach toward understanding the functions of polyP has been to identify and isolate the enzymes that synthesize and degrade polyP. Such enzymes have been identified in a variety of microorganisms. PolyP kinase, the enzyme that catalyzes the reversible transfer of the terminal phosphate from ATP to synthesize polyP, has been purified to homogeneity in several bacteria (3)(4)(5). Exopolyphosphatases that catalyze the hydrolysis of terminal phosphates from polyP have been purified from Escherichia coli (6), Corynebacterium xerosis (7), and Saccharomyces cerevisiae (8,9). Phosphotransferases that transfer a phosphate from polyP to AMP (10), NAD (11), glucose (12), and 1,3-diphosphoglycerate (13) have also been described. Endopolyphosphatases (PPN) also called polyP depolymerases or polyphosphorylases catalyze the non-processive cleavage of polyP to release intermediate-size chains during the course of the reaction. PPN are the least studied of the polyP-metabolizing enzymes and have been reported in species of Penicillium and Aspergillus and in S. cerevisiae (14 -16).During the course of investigating polyP metabolism in a variety of cells, we discovered PPN activities in organisms from archae to mammals but little or none among eubacteria. In this report, we describe the purification and characteristics of PPN from S. cerevisiae, where it is most abundant, using a mutant strain in which a major exopolyPase activity has been deleted (17). EXPERIMENTAL PROCEDURESCells and Tissues-S. cerevisiae CRX (17) was grown in YPD medium (1% yeast extract, 2% tryptone, 2% glucose) at 30°C to an A 600 of 14.5. The harvested cells were resuspended in an equal volume of 50 mM Tris-HCl, pH 7.5, 10% sucrose, frozen in liquid ni...

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“…Partially hydrolyzed polyP 750 was fractionated by 6% ureapolyacrylamide gel and then eluted from gel slices into 50 mM ammonium acetate, followed by ethanol precipitation (4).…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Endopolyphosphatases for Long Chain Inorganic Polyphosphate in Yeast and Mammals

Kumble

Kornberg

1996

Journal of Biological Chemistry

122

108

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“…The PPK of Propionibacterium shermanii like that of E. coli PPK has a subunit mass of 83 kDa and synthesizes polyP processively to a limit of about 750 residues, but unlike E. coli PPK appears to be monomeric (15,16). However, the glucokinase of P. shermanii, which utilizes polyP to phosphorylate glucose, is a homodimer of 33-kDa subunits (17) by either processive (polyP 700 ) or nonprocessive (polyP 30 ) mechanisms (18).…”

Section: Effects Of Chemical Agents On Ppk Activities-ementioning

confidence: 99%

The Multiple Activities of Polyphosphate Kinase ofEscherichia coli and Their Subunit Structure Determined by Radiation Target Analysis

Tzeng

Kornberg

2000

Journal of Biological Chemistry

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) at low ATP concentrations. Thus, the diverse functions of this enzyme involve different subunit organizations and conformations. The highly conserved homology of PPK among 18 microorganisms was used to determine important residues and conserved regions by alanine substitution, by site-directed mutagenesis, and by deletion mutagenesis. Of 46 single-site mutants, seven exhibit none of the five enzymatic activities; in one mutant, ATP synthesis from polyP is reduced relative to GTP synthesis. Among deletion mutants, some lost all five PPK activities, but others retained partial activity for some reactions but not for others.

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“…Iridium trifluoride has previously been produced by the reduction of IrF 4 with flowing SF 4 or with glass as a black solid with low yield [27], from conproportionation of IrF 6 /Ir [1] or the decomposition of IrF 4 at 400±450°C [1]. These routes lead to impure or poorly crystalline samples.…”

Section: Methodsmentioning

confidence: 99%