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At least 1,369 records · Page 76Linked to original sources
PubMed1984

Rapid efflux of Ca2+ from heart mitochondria in the presence of inorganic pyrophosphate.

Inorganic pyrophosphate (PPi) in the intracellular concentration range causes rapid efflux of Ca2+ from rat heart mitochondria oxidizing pyruvate + malate in a low Na+ medium. Half-maximal rates of Ca2+ efflux were given by 20 microM PPi. During and after PPi-stimulated Ca2+ efflux the mitochondria retain their structural integrity and complete respiratory control. Carboxyatractyloside inhibits PPi-stimulated Ca2+ efflux, indicating PPi must enter the matrix in order to promote Ca2+ efflux. Heart mitochondria have a much higher affinity for PPi uptake and PPi-induced Ca2+ efflux than liver mitochondria.

Animals↗
PubMed1988

Inorganic pyrophosphate: fructose-6-phosphate 1-phosphotransferase of the potato tuber is related to the major ATP-dependent phosphofructokinase of E. coli.

A procedure was developed for the purification of inorganic pyrophosphate: fructose-6-phosphate 1-phospho-transferase (PPi-PFK) from potato tubers. The enzyme has the structure alpha 4 beta 4 with a subunit of 68 kDa and a beta subunit of 60 kDa. The structural relationship of this enzyme to other PFKs and to fructose bisphosphatase was examined by immunoprecipitation and immunoblotting. Antibodies to the plant enzyme did not react with E. coli PFK. No cross-reaction was seen among the following enzymes or their antibodies: yeast fructose bisphosphatase; rabbit PFKs A, B, or the enzyme from brain; and the two subunits of the potato PPi-PFK. On the other hand, antibody to E. coli PFK-1 strongly cross-reacts with the 60 kDa polypeptide but not 68 kDa peptide.

Escherichia coli↗
PubMed1990

Effect of thyroid hormone on hepatic cholesterol 7 alpha hydroxylase, LDL receptor, HMG-CoA reductase, farnesyl pyrophosphate synthetase and apolipoprotein A-I mRNA levels in hypophysectomized rats.

The effects of thyroid hormone on cholesterol 7 alpha hydroxylase, LDL receptor, HMG-CoA reductase, apo A-I and farnesyl pyrophosphate synthetase hepatic mRNA levels were investigated in hypophysectomized rats. Of these mRNAs cholesterol 7 alpha hydroxylase responded the most rapidly and required the lowest dose of T3. Maximal mRNA levels were reached one hr after T3 administration and required 10 micrograms/100g of body weight. These results suggest that the hypocholesterolemic effect of thyroid hormone may be mediated by a primary effect on cholesterol 7 alpha hydroxylase gene expression.

Animals↗
PubMed1991

Protein phosphorylation by inorganic pyrophosphate in yeast mitochondria.

Inorganic pyrophosphate can function as phosphate donor in protein phosphorylation reactions in yeast mitochondria. It was shown that, when PPi substitutes for ATP as inhibitor of the pyruvate dehydrogenase reaction, maximal activity is reached after a lag-period of 30-60 minutes. 32P-labeling of peptides shows that [32P]PPi gives about 25% of the labeling obtained by [gamma-32P]ATP in the protein kinase reaction. The PPi dependent phosphorylation is increased several fold by the presence of cold ATP.

Adenosine Triphosphate↗
PubMed1993

Further studies on the antioxidant role of pyrophosphate in model membranes.

Our previous studies (G. Cervato et al., Chem. Phys. Lipids 56 (1990), 91-99) demonstrated that 100 microM pyrophosphate (PPi) inhibits Fe2+/ascorbate-induced peroxidation of arachidonic acid (AA) inserted in unilamellar liposomes (SUVs) of dipalmitoylphosphatidylcholine (DPPC), by chelating ferrous ions in the aqueous phase. In this work we demonstrate that the kinetics of AA peroxidation in DPPC SUVs are strongly affected by PPi, also at very low concentration (1 microM). In fact at low PPi concentration there is a longer lag-phase, while the maximum of thiobarbituric acid reactive substances (TBARS) is similar in both the presence and absence of 1 microM PPi. The lag-phase of peroxidation of AA in lysophosphatidylcholine (palmitoyl) (LysoPC) micelles is also prolonged. The AA peroxidation in membrane models without choline as the polar headgroup (dipalmitoylphosphatidylethanolamine (DPPE) SUVs, or Triton X-100 micelles), or in which AA is not free but esterified with glycerol (stearoyl-arachidonyl-phosphatidylcholine (SAPC)), is unaffected by the presence of 1 microM PPi.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1976

A rapid, enzymatic assay for measurement of inorganic pyrophosphate in biological samples.

An enzymatic assay for measurement of inorganic pyrophosphate (PPi) in biological samples is described using the UDPG pyrophosphorylase reaction and coupling it with three other enzymes in a system of phosphorylation and double reduction to form NADPH, which is measured fluorometrically. The method is specific for PPi in the presence of inorganic orthophosphate and can be used on small volumes of deproteinized ultrafiltrates of fluids or cell extracts. The assay was used here to determine the concentration of PPi in human plasma and serum, and the intracellular content of PPi in human skin fibroblasts, chondrocytes, and red blood cells. The mean PPi concentration of plasma was found to be 2.72 +/- 0.14 muM (mumo/l +/- S.E.M.); for serum it was 6.09 +/- 0.36 muM. The range (95% confidence limits) was 2.14-3.30 muM for plasma and 4.62-7.51 muM for serum. The average intracellular PPi content (pmoles PPi per 10(6) cells +/- S.E.M.) was as follows: (a) skin fibroblasts, 332 +/- 66; (b) articular chondrocytes, 655 +/- 46; red blood cells, 1.74 +/- 0.28.

Animals↗
PubMed1981

The effect of urine, pyrophosphate, citrate, magnesium and glycosaminoglycans on the growth and aggregation of calcium oxalate crystals in vitro.

The effects of pyrophosphate, citrate, magnesium, heparin and chondroitin sulphate on the growth and aggregation of calcium oxalate crystals were measured at concentrations likely to be found in 1% urine. The degrees of inhibition of growth and of aggregation caused by these compounds were related to the effects of normal 1% urine on these processes. It was concluded that chondroitin sulphate is responsible for the major portion of the inhibitory effect of urine on crystal aggregation, but that the effect on crystal growth is probably due to the additive or synergistic effects of a number of urinary constituents.

Adult↗
PubMed1982

Phosphoribosyl pyrophosphate synthetase and glutathione reductase in erythrocytes from hyperuricaemic and gout patients.

The enzymic activities of erythrocyte phosphoribosyl pyrophosphate synthetase (EC 2.7.6.1) and glutathione reductase (EC 1.6.4.2) have been measured in 54 primary gout patients, 35 individuals having hyperuricaemia and 51 healthy controls. Statistical analyses have shown a significant increase (p less than 0.01) in the enzymic activity of erythrocyte PRPP synthetase in both the hyperuricaemic and gout groups compared with the controls. No correlation between activity and age was found in any of the three clinical groups. A significant decrease (p congruent to 0.01) was found in the enzymic activity of red cell glutathione reductase in the gout group compared with the other two groups. The biochemical significance of the changes in enzymic activities of the two enzymes in primary gout is discussed.

Erythrocytes↗
PubMed1991

Raised urinary excretion of inorganic pyrophosphate in asymptomatic members of a hypophosphatasia kindred.

We report the screening of an Anglo-Welsh kindred in which two children were affected by different clinical forms of hypophosphatasia. Among the clinically normal adult members of the kindred, a raised urinary concentration of pyrophosphate was the commonest biochemical abnormality. The concentration of phosphate in serum was elevated in only one adult member of the kindred, the mother of the propositus. Consanguinity in this kindred suggests probable recessive inheritance, and the obligate heterozygotes each exhibited a low serum AP activity plus one other biochemical abnormality indicative of a carrier state.

Adult↗
PubMed1989

Molecular cloning and sequencing of human cDNA for phosphoribosyl pyrophosphate synthetase subunit II.

cDNA clones for human phosphoribosyl pyrophosphate synthetase subunit II (PRS II) were isolated. The five overlapping clones contained 2457 base pairs (bp) covering a 954-bp complete coding region for 318 amino acid residues. Homologies between human and rat PRS II were 99% of the amino acids and 88% of the nucleotides in the coding region. This amino acid homology seems to be the highest so far reported for enzymes involved in nucleotide metabolism and glycolysis. The highly conserved structure may be required for unique catalysis and rigid regulation of this enzyme.

Amino Acid Sequence↗
PubMed1989

Pyrophosphate analogues in pyrophosphorolysis reaction catalyzed by DNA polymerases.

It is demonstrated here that rat liver DNA polymerase beta catalyzes the pyrophosphorolysis reaction with pyrophosphate (PPi) and its analogues. The substrate specificity of the PPi-binding site of several DNA polymerases was investigated. It was discovered that the ability of DNA polymerases to utilize PPi analogues instead of PPi in the pyrophosphorolysis reaction was markedly restricted. Only imidodiphosphate and methylenediphosphonate were demonstrated as participating in this process. Oxodiphosphonate and phosphonoformate inhibited DNA synthesis, but probably not via the interaction with the PPi-binding site of DNA polymerases.

Animals↗
PubMed1991

Pyrophosphate-dependent phosphofructokinase, an anaerobic glycolytic enzyme?

Recent evidence indicates that in as diverse organisms as unicellular eukaryotes, higher plants and prokaryotes, anaerobic glycolysis relies on a pyrophosphate-dependent phosphofructokinase instead of the classical ATP-dependent enzyme. This difference in phosphoryl donor specificity does not necessarily reflect a primitive metabolism, as thought earlier, but could rather be the result of convergent evolution, fostered by the energetic advantage conferred to the cell when glycolysis is the sole source of ATP.

Adenosine Triphosphate↗
PubMed1992

Crucial role of pyrophosphate in the aminoacylation of E. coli tRNA(Phe) by yeast phenylalanyl-tRNA synthetase.

Rapid inactivation of the yeast phenylalanyl-tRNA synthetase in the course of aminoacylation of the heterologous E. coli tRNA(Phe) is observed. This inactivation occurs due to the formation of the tight complex of the enzyme with the pyrophosphate formed during the aminoacylation reaction. This complex is shown to be the normal intermediate of the reaction. Possible inactivation mechanism and correlation between structural differences of yeast and E. coli tRNAs(Phe) with the changes in the enzymatic mechanism of aminoacylation are discussed.

Acylation↗
PubMed1993

Diacylglycerol pyrophosphate, a novel phospholipid compound.

In studies on lipid kinase activities of microsomal membranes from cultured plant cells a new, hitherto unknown, lipid kinase product was detected. The new phospholipid, labeled by [gamma-32P]ATP, could be separated from known phospholipid species by thin layer chromatography using different solvent mixtures. After partial purification of the related enzyme activity, the substrate of the unknown lipid kinase was elucidated as phosphatidic acid. With authentic phosphatidic acid and partially purified enzyme, the lipid kinase product was prepared in mg quantities and its structure was determined by mass spectrometry and NMR analyses as diacylglycerol pyrophosphate, a hitherto unknown phospholipid. The possible physiological role of this novel phospholipid metabolite is discussed.

Cells, Cultured↗
PubMed1994

Oxygen exchange reactions catalyzed by vacuolar H(+)-translocating pyrophosphatase. Evidence for reversible formation of enzyme-bound pyrophosphate.

Vacuolar membrane-derived vesicles isolated from Vigna radiata catalyze oxygen exchange between medium phosphate and water. On the basis of the inhibitor sensitivity and cation requirements of the exchange activity, it is almost exclusively attributable to the vacuolar H(+)-pyrophosphatase (V-PPase). The invariance of the partition coefficient and the results of kinetic modeling indicate that exchange proceeds via a single reaction pathway and results from the reversal of enzyme-bound pyrophosphate synthesis. Comparison of the exchange reactions catalyzed by V-PPase and soluble PPases suggests that the two classes of enzyme mediate P(i)-HOH exchange by the same mechanism and that the intrinsic reversibility of the V-PPase is no greater than that of soluble PPases.

Diphosphates↗
PubMed1985

Conversion of dolichyl pyrophosphate N,N'-diacetylchitobiose to lipid-tri- to heptasaccharides by liver microsomes from hibernating ground squirrels (Citellus citellus L.).

Incubation of liver microsomes from hibernating ground squirrel with GDP-[14C]mannose and exogenous dolichyl phosphate resulted in the synthesis of dolichyl phosphate [14C]mannose. The mannosyltransferase activity was about 3-fold higher in microsomes from hibernating ground squirrels than in those from active animals. Incubation for 30 min of liver microsomes from hibernating animals with dolichyl pyrophosphate N,N'-diacetyl-[14C]chitobiose and GDP-[14C]mannose led to the synthesis of lipid-[14C]trisaccharide. When liver microsomes were incubated with lipid-[14C]trisaccharide and unlabelled GDP-mannose, lipid-tetra- to heptasaccharides were discovered in the chloroform-methanol (2:1) extract. Since, under the experimental conditions, negligible synthesis of dolichyl phosphate mannose was observed, it was assumed that GDP-mannose was a donor of mannose in the conversion of lipid-trisaccharide into lipid-oligosaccharides containing 2-5 mannose residues.

Animals↗
PubMed1979

Is the d an allelic gene of D in the Rh blood group system? A quantitative study using 99mTechnetium-pyrophosphate-labelled antibody (TcLA) method.

This article reports on studies of Rh antigens, such as D, Du and d, using uranyl-labelled antibody (ULA) and TcLA (99mTc-pyrophosphate-labelled antibody) methods for the first time for this purpose. TcLA method proved to be simple in labelling and very sensitive (20--100 times more so than the indirect Coombs test) in the detection of Rh antigen-antibody binding. Results of this quantitative study demonstrate convincingly that the d is not an allelic gene of D but rather the weakest of the series D less than Du less than d. Although the evidence from this study demonstrates clearly that differences between D and d are only quantitative, the authors do not think that the Rh nomenclature should be changed but they do think that the present evidence should be used in regard to the understanding of the allelism in the Rh blood group system. The c is an allelic gene of C as the e is an allelic gene of E; specific test sera detecting every one of these antigens exist and the family studies verify these statements. However, the d is not a distinct antigen as c and e are, even if the pattern of inheritance from family studies, using the existent anti-D serum, would suggest the allelism as probability. That is why in the past the anti-Du and anti-d specific test sera never incidentally found or artificially produced.

Alleles↗
PubMed1992

Homogeneous phase pyrophosphate (PPi) measurement (H3PIM). A non-radioactive, quantitative detection system for nucleic acid specific hybridization methodologies including gene amplification.

A one-step, non-radioactive, homogeneous phase revelation system designed to detect and quantify nucleic acid hybridization is described. The principle of the procedure, termed homogeneous phase pyrophosphate (PPi) measurement (H3PIM), is to detect and quantify the release of PPi from nucleotides, which occurs stoichiometrically when nucleic acids are synthesized. The method does not require any special reagents before the H3PIM revelation step. H3PIM is particularly adapted to quantitative measurement of gene amplification or cDNA gene expression using PCR, but can also be used following random priming or simultaneous multi-step nucleic acid amplification. This rapid, sensitive, liquid phase procedure permits the design of low-cost, fully automated devices for gene detection and quantification.

DNA↗