SEARCH · PubMed Health

Results for “Pyrophosphatases”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources

PubMed1978

[Change in inorganic pyrophosphatase during maturation and aging of red blood cells from newborns].

The activity of inorganic pyrophosphatase (PPase) of red blood cells (rbc) from newborns is about 40% higher than that of adults. To answer the question whether the higher activity was due to the enhanced reticulocyte count of the newborn's cell population, the rbc of both newborns and adults were separated into different density subpopulations by means of isopycnic density gradient centrifugation in dextran. To judge the quality of separation in the individual age populations of rbc, the activity of glucose-6-phosphate dehydrogenase (G-6-PD) and the reticulocyte count were determined. The activity fall of PPase during maturation and aging of rbc is stronger than that of G-6-PD. The density subpopulations of rbc from newborns and adults with equal reticulocyte counts show the same PPase activities yet different G-6-PD activities. Obviously, the higher PPase activity of a cell population of newborns is due to the higher proportion of reticulocytes. The inorganic PPase is well suited as a guiding criterion to judge the maturity and age of rbc of newborns.

Adult↗

PubMed1994

ZIO impregnation and cytochemical localization of thiamine pyrophosphatase and acid phosphatase activities in small granule-containing (SGC) cells of rat superior cervical ganglia.

Cytochemical relationship between Golgi complex and dense-cored granules (DCGs) of small granule-containing (SGC) cells in rat superior cervical ganglia was examined in electron microscopy by zinc-iodide-osmium tetroxide (ZIO) method and by enzyme cytochemistry for thiamine pyrophosphatase (TPPase) and acid phosphatase (ACPase). After ZIO impregnation, all the saccules of Golgi apparatus and some of tubular rough endoplasmic reticulum (rER) were stained. DCGs in periphery of SGC cells were not stained, but varying degrees of dense deposits occurred in the DCGs in vicinity of Golgi trans-saccules. Both TPPase and ACPase activities were localized in one or two stacked layers of saccules on the trans side of the Golgi complex. No reaction products were demonstrated in the DCGs. From these results, we suggest that the DCGs of SGC cells in rat superior cervical ganglia are derived from the Golgi complex, and that lysosomal cleavage of protein contents in the DCGs may occur in the trans Golgi saccules.

Acid Phosphatase↗

PubMed1995

[H+-ATPase and H+-pyrophosphatase in yeast vacuolar membrane].

Saccharomyces carlsbergenis vacuoles possess an ATPase activity differing from those of the well-known H(+)-ATPase of plasma membranes and mitochondria as well as from those of other phosphohydrolases. Yeast vacuolar ATPase represents an electrogenic H(+)-translocase. H(+)-ATPase was incorporated into a liposomal membrane in a functionally active form. Tonoplast ATPase did not form a phosphorylated intermediate. Purified vacuolar ATPase contained three major polypeptides with M(r) of 72, 62 and 16 kDa. S. carlsbergensis vacuoles also contained a pyrophosphatase (PPase) whose properties differed significantly from those of other vacuolar phosphohydrolases. Vacuolar membrane-bound PPase is a proton pump; its molecular mass is about 120 kDa. The enzyme molecule consists of three subunits, each of M(r) = 41 kDa. Soluble PPase from vacuolar sap has a molecular mass of about 82 kDa and consists of three subunits of M(r) = 28 kDa.

Intracellular Membranes↗

PubMed1994

[Implications of alkaline phosphatase pyrophosphatase activity: intracellular functions of alkaline phosphatase].

We demonstrated that polyamines, such as spermine and spermidine, can enhance the pyrophosphatase (PPase) activity of alkaline phosphatase (ALP). Bisphosphonates such as disodium-1-hydroxy-1-aminopropylidine-1,1-diphosphonate (APD) and ethane-1-hydroxy-1,1'-diphosphonate (HEDP) inhibited ALP phosphate ester hydrolysis activity more than PPase activity at the same concentrations. This indicated that PPase activity of ALP was available in the presence of pyrophosphate analogues and possibly organic pyrophosphates as well. Vanadate and cadmium inhibited ALP and PPase activity more than ALP phosphate ester hydrolysis activity at the same concentrations. Calcium inhibited ALP PPase activity, though it did not inhibit ALP phosphate ester hydrolysis activity. At high concentrations, ascorbic acid slightly inhibited ALP PPase activity, though it did not inhibit ALP phosphate ester hydrolysis activity. ALP PPase activity appeared to have ubiquitous intracellular existence, broad substrate specificity and extensive interaction with calcium, vanadium and polyamines-substances which are important for cell metabolism and cell growth. These findings suggested that intracellular ALP modulated cell metabolism and cell growth by its PPase activity.

Alkaline Phosphatase↗

PubMedDate not supplied

[Localization of a structural locus of erythrocyte inorganic pyrophosphatase on chromosome 10 in man by the method of human-hamster cellular hybridization].

The study of man-hamster hybrids puts forward a correlation between the activity of the erythrocyte inorganic pyrophosphatase and the presence of the human chromosome C 10, and on the other hand, a very positive correlation between the activity of this enzyme with the soluble glutamate-oxaloacetate transaminase (GOTS), already localized on the same chromosome.

Animals↗

PubMed1993

Surface charge modifications do not affect the hydrolytic activity of membrane-bound pyrophosphatase of Rhodospirillum rubrum.

The surface charge of the membrane of chromatophores of Rhodospirillum rubrum was modified by two methods: fusion of liposomes with the membrane of the chromatophore by changing the pH and by incubating chromatophores in the presence of cationic or anionic detergents. The hydrolytic activity of membrane-bound pyrophosphatase, on surface charge modified chromatophores, did not change the Km of the enzyme for its substrate (Mg-PPi2-) nor the activation effect of free Mg2+ on the hydrolytic activity. This membrane enzyme is not regulated by surface charge.

Bacterial Chromatophores↗

PubMed1996

Specific ADP-ribose pyrophosphatase from Artemia cysts and rat liver: effects of nitroprusside, fluoride and ionic strength.

One specific ADP-ribose pyrophosphatase (ADPRibase) has been identified in Artemia cysts, following a protocol that in rat liver allows the identification of three ADPRibases. Artemia ADPRibase resulted similar, but not identical, to rat liver ADPRibase-I with respect to known and novel properties disclosed in this work. In the presence of Mg2+, Artemia ADPRibase was highly specific for ADP-ribose and showed a low, 0.7 microM Km. Preincubation with the nitric oxide donor nitroprusside and dithiothreitol, elicited dose- and time-dependent, severalfold increase of Km and decrease of Vmax. At saturating ADP-ribose concentrations, fluoride was a strong inhibitor (IC50 approximately equal to 10-20 microM), whereas bringing ionic strength to 0.3-1.3 mol/l doubled the activity measured at lower or higher strengths. The novel fluoride and ionic strength effects were studied also with rat liver ADPRibase-I. Differences between the Artemia enzyme and ADPRibase-I concerned molecular weight (31,000 versus 38,500, respectively), Mn2+ ability to substitute for Mg2+ as the activating cation (better for the rat enzyme), and Vmax decrease by nitroprusside (not seen with the rat enzyme). The results are discussed in relation with the role of specific ADPRibases as protective factors limiting free ADP-ribose accumulation and protein glycation, and as targets for cytotoxic agents.

Animals↗

PubMed1997

dUTP pyrophosphatase as a potential target for chemotherapeutic drug development.

Aberrant dUTP metabolism plays a critical role in the molecular mechanism of cell killing induced by inhibitors of dihydrofolate reductase and thymidylate synthase. While considerable effort has been directed towards discovering new, more potent inhibitors of these two enzymes, little attention has been given dUTP pyrophosphatase (dUTPase)--the key modulator of cellular dUTP levels--as a potential target for chemotherapeutic drug development. Recent studies have provided evidence that dUTPase is vital for cellular and, in some cases, viral DNA replication. Furthermore, some retroviruses encode dUTPases--a fact which suggests that cellular dUTP metabolism may be more important than previously realized. Here, we briefly review current knowledge of cellular and viral dUTPases and discuss the potential of these enzymes as targets for cancer chemotherapeutic and anti-viral drug development.

Animals↗

PubMed1998

Characterization of thiamine pyrophosphatase positive phagocytic cells in the neural lobe of rat pituitary.

Here, using a histochemical staining for a microglia/phagocyte marker TPP-ase (Murabe, Sano 1981), and an electron microscopy we characterized the population of pituitary phagocytic cells activated by cerebral ischemia. An intense thiamine pyrophosphatase (TPP-ase) activity was demonstrated in glial cells and some cells of blood vessels of neural lobe, late period (12 months) after experimental ischemia. TPP-ase positive cells were ultrastructurally identified as pituicytes, microglia, pericytes and perivascular cells. The product characteristic for TPP-ase activity was seen on plasma membrane of these cells. Our electron-microscopic histochemical results provide strong support for a role of pituicytes, pericytes and perivascular cells as a phagocytic cells involved in mechanism of elimination of ischemically damaged axonal endings in neural lobe.

Animals↗

PubMed1998

Growth-related expression of the ectonucleotide pyrophosphatase PC-1 in rat liver.

Plasma cell differentiation antigen-1 (PC-1) is a 5'-ectonucleotide pyrophosphatase that has been implicated in various processes including insulin- and nucleotide-mediated signaling and cell growth. We show here that the expression of both PC-1 mRNA and protein in rat liver and in hepatoma cells is strictly growth-related. Thus, the level of PC-1 in FAO hepatoma cells increased with the cell density. PC-1 was not expressed in the neonatal rat liver, but gradually appeared in the first weeks of age, to reach adult levels around the weaning period. Furthermore, PC-1 protein and mRNA largely disappeared from the liver within 24 hours following a hepatectomy of 70%, but re-appeared in the later phases (3-15 days) of the ensuing regeneration period. An equally rapid loss of PC-1 protein and mRNA could also be provoked in normal livers by the administration of the translational inhibitor, cycloheximide, but the transcriptional inhibitors, actinomycin D and alpha-amanitin, did not show these effects. Nuclear run-on assays revealed that the loss of PC-1 mRNA after hepatectomy or after the administration of cycloheximide was not caused by a decreased transcription of the PC-1 gene, suggesting that the level of PC-1 is controlled by an mRNA-stabilizing protein that is lost after hepatectomy and has a high turnover.

Aging↗

PubMed1997

Determination of inorganic phosphate by coupling thymidine phosphorylase and reversed-phase high-performance liquid chromatography: application to tonoplast pyrophosphatase activity.

We developed an HPLC method for the measurement of inorganic phosphate using thymidine phosphorylase (EC 2.4.2.4). This enzyme catalyzes the phosphorolysis of thymidine to 2-deoxyribose 1-phosphate and thymine. Thymine release was measured at 265 nm after separation by reverse-phase HPLC. The assay was sensitive enough to detect as little as 10 pmol of Pi. The response to the phosphate concentration was linear from 1 to 100 microM. The value of this method was demonstrated in an analysis of the kinetics of Pi release from PPi in the presence of Catharanthus roseus tonoplast pyrophosphatase.

Chromatography, High Pressure Liquid↗

PubMed1980

Kinetics of a nucleotide pyrophosphatase in the plasma membrane of the fat cell.

Fat cells from rat and rabbit hydrolyzed externally applied adenosine triphosphate at a rate of about 1.8 nmol times mg(-1) cells times min(-1) corresponding to about 0.3 mumol times mg(-1) protein tinus min(-1). Similar activities were found in cell homogenates. In purified adipocyte plasma membranes the rate of hydrolysis was about 1.8 mumol times mg(-1) protein times min(-1). The hydrolytic activity was dependent on divalent metal ions. Mg(2+), Mn(2+) and Ca(2+) gave highest activities. The activity was maximal at about equimolar concentrations of M(2+) and ATP. Km for MgATP was about 0.23 mM and for CaATP about 0.36 mM. Combinations of Mg(2+) and Ca(2+), or of Mg(2+), Na(+) and K(+) gave similar activities as did Mg(2+) only. At concentrations of 1 mM the following nucleotides were hydrolyzed with a decreasing rate: ATP > ITP > GTP > UTP = CTP. In isolated fat cells the beta-adrenergic drug isoproterenol and insulin slightly increased the rate of hydrolysis of external ATP, while the alpha-effector clonidine was inhibitory. The results suggest that a major portion of the ATP hydrolytic activity of the fat cell plasma membrane represents a nucleotide pyrophosphatase activity with access to externally applied ATP.

Adenosine Triphosphatases↗

PubMed1976

Serum alkaline phosphatase, nucleotide pyrophosphatase, 5'-nucleotide and lipoprotein-X in cholestasis.

The nature of the stationary band of alkaline phosphatase, which occurs on starch gel electrophoresis of sera from patients with biliary obstruction, has been examined. Stationary alkaline phosphatase was eluted from Sepharose 4-B gel close to the void volume and together with the plasma membrane enzymes, nucleotide pyrophosphatase and 5'-nucleotidase, and with lipoprotein-X. Electron microscopy of concentrates of stationary alkaline phosphatase, prepared by ultracentrifugation and gel filtration, showed large (0.3--1 mum diameter) and small structures (30-70 nm diameter) by negative staining. The activity of the stationary alkaline phosphatase was associated in fixed sections with particles of about 10 nm X 40 nm resembling those of lipoprotein-X. It is suggested that the stationary alkaline phosphatase does not move into starch gel during electrophoresis because it is particulate. In agar electrophoresis the alkaline phosphatase which was stationary on starch gel moved towards the cathode with lipoprotein-X.

Adult↗

PubMed1992

Vacuolar H(+)-translocating pyrophosphatases: a new category of ion translocase.

The membrane surrounding the central vacuole of plant cells contains an H(+)-translocating ATPase (H(+)-ATPase) and an H(+)-translocating inorganic pyrophosphatase (H(+)-PPase). Both enzymes are abundant and ubiquitous in plants but the H(+)-PPase is unusual in its exclusive use of inorganic pyrophosphate (PPi) as an energy source. The lack of sequence identity between the vacuolar H(+)-PPase and any other characterized ion pump implies a different evolutionary origin for this translocase. The existence of the vacuolar H(+)-PPase, in conjunction with increasing recognition of PPi as a key metabolite in plant systems, necessitates reconsideration of ATP as the primary energy source for membrane transport in plant cells.

Amino Acid Sequence↗

PubMed2000

Distinct isoforms of ADPglucose pyrophosphatase and ADPglucose pyrophosphorylase occur in the suspension-cultured cells of sycamore (Acer pseudoplatanus L.).

The intracellular localizations of ADPglucose pyrophosphatase (AGPPase) and ADPglucose pyrophosphorylase (AGPase) have been studied using protoplasts prepared from suspension-cultured cells of sycamore (Acer pseudoplatanus L.). Subcellular fractionation studies revealed that all the AGPPase present in the protoplasts is associated with amyloplasts, whereas more than 60% of AGPase is in the extraplastidial compartment. Immunoblots of amyloplast- and extraplastid-enriched extracts further confirmed that AGPase is located mainly outside the amyloplast. Experiments carried out to identify possible different isoforms of AGPPase in the amyloplast revealed the presence of soluble and starch granule-bound isoforms. We thus propose that ADPglucose levels linked to starch biosynthesis in sycamore cells are controlled by enzymatic reactions catalyzing the synthesis and breakdown of ADPglucose, which take place both inside and outside the amyloplast.

Cell Culture Techniques↗

PubMed2001

Partial characterization of H-translocating inorganic pyrophosphatase from 3 citrus varieties differing in vacuolar pH.

Vacuolar pyrophosphatase (V-PPase) from juice cells of 3 citrus varieties (differing in their vacuolar pH) were partially characterized using purified tonoplast vesicles. Total V-PPase activity was highest in vesicle samples from sweet limes with vacuolar pH of 5.0, while samples from acid limes (with lowest vacuolar pH of 2.0) had the minimal total V-PPase activity. Samples from 'Valencia' orange had intermediate V-PPase levels. When assayed at equal V-PPase activity (measured as Pi production), V-PPase was not able to generate a pH gradient (DeltapH) in vesicles from acid lime, despite its capacity to form a DeltapH in the presence of ATP. Vesicles from sweet lime and 'Valencia' orange were able to form similar DeltapHs in the presence of PPi and ATP supplied together or separately. Antibodies raised against a peptide corresponding to the catalytic site of mung bean V-PPase reacted with samples from all varieties, coinciding with their capacity to hydrolyze PPi. However, antibodies raised against the entire V-PPase polypeptide from mung bean recognized V-PPase from sweet lime and 'Valencia' orange, but did not recognize acid lime samples even at elevated protein concentrations. The structural differences highlighted by antibody recognition, substrate affinity and proton-pumping reactions of V-PPase presented here may reflect evolutionary adaptations related to its reduced function under in vivo conditions and are in agreement with our understanding of acid, sugar accumulation and vacuolar pH changes during the development and maturation of citrus fruits.

Journal Article↗

PubMed1968

The pyrophosphatase activity of pig kidney alkaline phosphatase and its inhibition by magnesium ions and excess of pyrophosphate.

1. Pig kidney enzyme resembles other non-specific alkaline phosphatases in its ability to hydrolyse inorganic pyrophosphate (PP(i)). 2. Studies of enzyme velocity as a function of PP(i) concentration show that Michaelis-Menten kinetics are obeyed when a constant PP(i)/Mg(2+) concentration ratio is maintained, but velocity-substrate concentration curves are sigmoid when the concentration of PP(i) is increased but that of Mg(2+) is kept constant. The enzyme is inhibited when the total PP(i) concentration is greater than the total concentration of Mg(2+). Pyrophosphatase activity is activated by Mg(2+), but if the concentration of the metal ion is increased to a value in excess of the total PP(i) concentration Mg(2+) is then strongly inhibitory. 4. It appears that the enzyme is most active towards the complex ion MgPP(i) (2-). The enzyme probably hydrolyses PP(i) (4-) also, but this is a poorer substrate and its competition with MgPP(i) (2-) leads to inhibition. At high Mg(2+) concentrations Mg(2)PP(i) is formed. This complex appears to be a potent inhibitor. 5. Sigmoid plots of v against s and of v against i result from interactions occurring between Mg(2+) and PP(i) (4-) leading to MgPP(i) (2-) and Mg(2)PP(i), and are not indicative of allosteric behaviour.

Alkaline Phosphatase↗

PubMed1983

Increased glycosylation capacity in regenerating rat liver is paralleled by decreased activities of CMP-N-acetylneuraminate hydrolase and UDP-galactose pyrophosphatase.

In regenerating rat liver the activities of CMP-N-acetylneuraminate hydrolase and UDP-galactose pyrophosphatase were decreased to 40-50% of control values within 35 h after partial hepatectomy. In the same time period the activities of sialyltransferase and galactosyltransferase were increased, and the initial sharp decrease in the carbohydrate content of liver and serum glycoproteins was largely restored. The antiparallel nature of these events is suggestive of an involvement of nucleotide-sugar-hydrolysis enzymes in rat liver glycoprotein biosynthesis.

Animals↗