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PubMed1982

Conversion of amorphous tricalcium phosphate into apatitic tricalcium phosphate.

Precipitated calcium orthophosphate, rapidly prepared in highly supersaturated solutions at pH 9-11, is an amorphous tricalcium orthophosphate (atomic ratio Ca/P = 3/2) of formula Ca9(PO4)6, nH2O. Kept wet at room temperature, this phosphate is hydrolyzed according to the reaction PO4(3-) + H2O leads to HPO4(2-) + OH-; a tricalcium orthophosphate series is then formed, its general formula is Ca9 (HPO4)x (PO4)6-x (OH)x, O less than or equal to x less than or equal to 1. Moreover, the amorphous phosphate is converted into apatitic phosphate at half hydrolysis (x approximately equal to 0.5). The hydrolysis occurs simultaneously with an endothermic effect [delta H = 12.0 +/- 2.0 kJ/mol Ca9(PO4)6], and the conversion with an exothermic effect [delta H = -5.9 +/- 1.0 kJ/mol Ca9(PO4)6].

Calcium Phosphates↗
PubMed1981

A simple screening procedure for glucose phosphate isomerase, phosphofructokinase, aldolase and glyceraldehyde-3-phosphate dehydrogenase deficiencies.

A simple screening procedure for the detection of glucose-phosphate isomerase (GPI), phosphofructokinase (PFK), aldolase (AL) and glyceraldehyde-3-phosphate dehydrogenase (GAPD) deficiencies in blood, is described. These enzymes catalyze the second, third, fourth, and sixth reactions in the Embden-Meyerhof pathway. The procedure is based on the conversion of glucose-6-phosphate to 1,3-diphosphoglycerate (1,3-DPG) which is catalyzed by the sequential action of the GPI, PFK, AL and GAPD. The presence of the enzyme activities is visually estimated by the reduction of NAD+ (non-fluorescent) to NADH (fluorescent) which occurs when 1,3-DPG is formed. Absence of fluorescence indicates the deficiency of anyone of the four enzymes, which are specified by using separately the PFK, AL and GAPD respective substrates.

Anemia, Hemolytic, Congenital↗
PubMed1983

Posttraumatic hypophosphataemia and urinary phosphate excretion with and without phosphate supplementation. An experimental study in pigs.

Hypophosphataemia commonly follows trauma of various types. Several aetiologic factors have been proposed and the clinical significance of posttraumatic hypophosphataemia has been discussed. For study of the mechanisms underlying hypophosphataemia associated with surgical trauma, an experimental model has been developed which permits induction of hypophosphataemia under standardized conditions in anaesthetized and traumatized pigs. In the present study this model was used to investigate the relationship between posttraumatic hypophosphataemia and urinary excretion of with or without phosphate supplementation. The results suggest that the adrenaline release associated with stress and trauma induced an immediate and rapid fall in the serum phosphate (S-P) level. The abrupt fall was followed after 24 hours by a slower decrease. This second phase of S-P decrease was not induced by catecholamine release or by glucose infusion and was not prevented by phosphate supplementation. It appeared to be related to an inadequate renal response to the hypophosphataemia, i.e. a relative phosphaturia. The cause of this phosphaturia is not fully understood, but both extracellular volume expansion and the humoral response to trauma are possible explanations.

Animals↗
PubMed1995

The cation-independent mannose-6-phosphate receptor binds to soluble GPI-linked proteins via mannose-6-phosphate.

The cation-independent mannose-6-phosphate/insulin-like growth factor II receptor has been observed to bind to soluble forms of glycosyl-phosphatidylinositol-linked molecules, one of mammalian origin (rat Thy-1) and two of protozoan origins. Of the two phosphate groups found on the soluble forms of the protozoan glycosyl-phosphatidylinositol-linked molecules: (i) the internal mannose-6-phosphate diester (which forms a part of the ethanolamine bridge) and (ii) the inositol-1,2 cyclic phosphate group (which arises after cleavage of the membrane associated form with phosphatidylinositol-specific phospholipase C), only the former appears to be recognized by the mannose-6-phosphate/insulin-like growth factor II receptor, as mild acid hydrolysis which destroys the latter has been observed not to affect the receptor binding site.

Animals↗
PubMed1997

Serum calcium, phosphate and alkaline phosphate levels in epileptic children treated with phenobarbitone.

A longitudinal study to estimate the serum calcium, phosphate and alkaline phosphatase levels of 89 ambulatory epileptic children, aged between 3 years and 12 years, and having generalised tonic-clonic seizures, was carried out. None was on any form of medication for the treatment of seizures prior to presentation. Each patient received only phenobarbitone during the period of study. Serum levels of the biochemical parameters were determined at presentation, 6 months and 12 months, while serum phenobarbitone levels were estimated at 6 months and 12 months. Mean serum calcium, phosphate and alkaline phosphatase of the patients remained within the normal range. Using the paired 't' test, the differences in the levels of the parameters at the three measurements were not statistically significant (P > 0.05). Serum phenobarbitone levels remained within the therapeutic range during the period of study. Our results show that over a 12-month period, serum levels of calcium, phosphate, and alkaline phosphatase, remain normal in ambulant epileptic children treated with phenobarbitone.

Alkaline Phosphatase↗
PubMed1990

Adsorption of 5'-adenosine monophosphate onto precipitated calcium phosphate: effects of inorganic polyphosphates and carbamyl phosphate.

In this paper it is shown that the adsorption of 5'-adenosine monophosphate (5'-AMP) onto precipitated calcium phosphate exhibits a sigmoidal profile as revealed by isotherms at 45 degrees C. This result indicates a cooperative behavior in the adsorption of 5'-AMP. The relationship between adsorption capacity and surface area of the sedimented matrix may be interpreted as an indication that there is a monolayer of the absorbed nucleotide on the solid surface. The pH dependence of adsorption suggests that the negatively charged phosphoryl group of 5'-AMP interacts with a positively charged site (possibly Ca2+) on the matrix surface. The adsorption of the nucleotide is markedly decreased at pH values above 8.0. The Dixon-like plot of the effect of pH suggests an inhibitory role of hydroxyl ions in the adsorption of 5'-AMP. At pH 7.5, other anions such as pyrophosphate, tripolyphosphate and carbamyl phosphate also inhibit the adsorption of the nucleotide, probably by interacting with its adsorption site. We suggest that these phosphorylated molecules could have played a role in chemical evolution by modulating the amount of nucleotides adsorbed onto mineral surfaces. The significance of these phenomena in chemical evolution is discussed.

Adenosine Monophosphate↗
PubMed1997

Two cDNAs from potato are able to complement a phosphate uptake-deficient yeast mutant: identification of phosphate transporters from higher plants.

Acquisition as well as translocation of phosphate are essential processes for plant growth. In many plants, phosphate uptake by roots and distribution within the plant are presumed to occur via a phosphate/proton cotransport mechanism. Here, we describe the isolation of two cDNAs, StPT1 and StPT2, from potato (Solanum tuberosum) that show homology to the phosphate/proton cotransporter PHO84 from the yeast Saccharomyces cerevisiae. The predicted products of both cDNAs share 35% identity with the PHO84 sequence. The deduced structure of the encoded proteins revealed 12 membrane-spanning domains with a central hydrophilic region. The molecular mass was calculated to be 59 kD for the StPT1 protein and 58 kD for the StPT2 protein. When expressed in a PHO84-deficient yeast strain, MB192, both cDNAs complemented the mutant. Uptake of radioactive orthophosphate by the yeast mutant expressing either StPT1 or StPT2 was dependent on pH and reduced in the presence of uncouplers of oxidative phosphorylation, such as 2,4-dinitrophenol or carbonyl cyanide m-chlorophenylhydrazone. The K(m) for Pi uptake of the StPT1 and StPT2 proteins was determined to be 280 and 130 microM, respectively. StPT1 is expressed in roots, tubers, and source leaves as well as in floral organs. Deprivation of nitrogen, phosphorus, potassium, and sulfur changed spatial expression as well as the expression level of StPT1. StPT2 expression was detected mainly in root organs when plants were deprived of Pi and to a lesser extent under sulfur deprivation conditions. No expression was found under optimized nutrition conditions or when other macronutrients were lacking.

Amino Acid Sequence↗
PubMed2006

A novel type of membrane based on cholesteryl phosphocholine, cholesteryl phosphate, or sitosteryl phosphate, and dimyristoylglycerol.

Mixtures of amphiphilic cholesteryl phosphate (CP), sitosteryl phosphate (SP), or cholesteryl phosphocholine (CPC) with the nonphosphoryl diacyl lipid dimyristoylglycerol (DMG) or with cholesterol give self-organized systems (giant vesicles) in a wide range of pH, as demonstrated by fluorescence microscopy, differential scanning calorimetry, and small-angle X-ray scattering. The water permeability of a 1 : 1 molar mixture of CPC and DMG was also measured by a stopped-flow/light-scattering method. The novel self-organized systems are akin to natural eukaryotic ones, the only difference being the site of the phosphate-containing head-group, located on cholesterol instead of DMG. They might be present in some organisms not yet studied for the composition of their membranes.

Cholesterol Esters↗
PubMed1981

Glucose 6-phosphate dehydrogenase variants: a unique variant (G6PD Kobe) showed an extremely increased affinity for galactose 6-phosphate and a new variant (G6PD Sapporo) resembling G6PD Pea Ridge.

Two new glucose 6-phosphate dehydrogenase (G6PD) variants associated with chronic nonspherocytic hemolytic anemia were discovered, G6PD Kobe was found in a 16-year-old male associated with hemolytic crisis after upper respiratory infection. The enzyme activity of the variant was about 22% of that of the normal enzyme. The main enzymatic characteristics were slower than normal anodal electrophoretic mobility, high Km G6P, increased thermal-instability, an acidic pH optimum, and an extremely increased affinity for the substrate analogue, galactose 6-phosphate (Gal-6P). G6PD Sapporo was found in a 3-year-old male associated with drug-induced hemolysis. The enzyme activity was extremely low, being 3.6% of normal. In addition, this variant showed high Ki NADPH and thermal-instability. G6PD Kobe utilized the artificial substrate Gal-6P effectively as compared with the common natural substrate, glucose 6-phosphate. In G6PD Sapporo, NADPH could not exert the effect of product inhibition. The structural changes of these variants are expected to occur at the portions inducing conformational changes of the substrate binding site of the enzyme.

Adolescent↗
PubMed1991

A synthetic study on cyclic phosphate derivatives of seconucleosides as potential antiviral agents (I). Synthesis of 3',5'-cyclic phosphates of 2'-substituted secouridines and secoribavirins.

The synthetic study of 3',5-cyclic phosphates of 2'-substituted 2',3'-secouridines and 2',3'-secoribavirins toward development of new antiviral agents is described. These cyclic phosphates were synthesized from their respective 4-nitrophenyl 3',5'-cyclic phosphate triesters. These triesters were prepared from the corresponding 2'-azido and 2'-bromo 2',3'-seconucleosides.

Antiviral Agents↗
PubMed1983

Formation of novel nucleosides from free base and sugar phosphate: aqueous reaction of 2-aminopyrimidine and ribose-5-phosphate.

The facile formation of glycosylamines suggests that a base liberated by depurination might react at the free C1 position of the sugar phosphate from which it had been hydrolyzed, effectively repurinating the site. Model experiments testing this hypothesis demonstrate that such a reaction does take place. The primary product of a reaction between 2-aminopyrimidine (a model for guanine) and ribose-5-phosphate is characterized by enzymatic and chemical degradation, and UV spectra. It is shown to be a novel nucleoside with the base attached via its exocyclic amino group to the C1 of the ribose-5-phosphate.

5'-Nucleotidase↗
PubMed1986

Permeability of bilayer lipid membranes in phase transition. The significance of intermolecular phosphate-phosphate hydrogen bonding.

The effect of pH on the phase transition temperature of 1,2-dipalmitoyl-sn-glycero-3-phosphate (DPPA) and 1,2-dipalmitoyl-sn-glycero-3-thionphosphate (thion-DPPA) has been investigated. The phase transition was detected using the jump like increase effect in the conductance of the planar bilayer membrane. It is shown that the steepness of pH-dependence of the phase transition temperature differs for these two kinds of lipids in the pH range of 3.5-8. This result is explained in terms of decreased intermolecular hydrogen bonding between the head groups of thion-DPPA. Calculations taking into account the ability of DPPA molecules to intermolecular phosphate-phosphate hydrogen bonding were made. The results of calculations are in good agreement with the experimental data obtained in this study.

Hydrogen Bonding↗
PubMed1995

Effects of an aldose reductase inhibitor on erythrocyte fructose 3-phosphate and sorbitol 3-phosphate levels in diabetic patients.

Fructose 3-phosphate and sorbitol 3-phosphate are novel metabolites that have been shown to associate with the polyol pathway in animal experiments. Fructose 3-phosphate is of particular interest because of its potent glycation capability as compared with other glycolytic intermediates, e.g., fructose. We observed the effects of treatment with epalrestat, an aldose reductase inhibitor, on their concentrations in erythrocytes from diabetic patients. The levels of both metabolites were significantly higher in diabetic patients than in non-diabetic subjects. A group of patients who had been treated with epalrestat showed significantly lower levels of both metabolites as compared with those untreated. A treatment of three patients with epalrestat for one month resulted in obvious decreases in their concentrations. The results suggest a possible explanation for the preventive effect of an aldose reductase inhibitor on nonenzymatic glycation.

Adult↗
PubMed1983

Evidence for the homology of hexose 6-phosphate dehydrogenase and glucose 6-phosphate dehydrogenase: comparison of the amino acid compositions.

Amino acid compositions of hexose 6-phosphate dehydrogenase and glucose 6-phosphate dehydrogenase from crucian carp and rat, and that of sea-urchin glucose 6-phosphate dehydrogenase were compared in order to ascertain if they are homologous enzymes. The results demonstrated that the overall amino acid compositions of the two enzymes remarkably resemble each other, and that the composition divergence (D = 0.038) of the crucian carp enzymes is in the range of those for homologous proteins so far reported. These findings strongly support our previous prediction that the two enzymes have diverged from a common ancestral molecule.

Amino Acids↗
PubMed2005

Synthesis of arabinitol 1-phosphate and its use for characterization of arabinitol-phosphate dehydrogenase.

D-arabinitol 1-phosphate (Ara-ol1-P), a substrate for D-arabinitol-phosphate dehydrogenase (APDH), was chemically synthesized from D-arabinonic acid in five steps (O-acetylation, chlorination, reduction, phosphorylation, and de-O-acetylation). Ara-ol1-P was used as a substrate for the characterization of APDH from Bacillus halodurans. APDH converts Ara-ol1-P to xylulose 5-phosphate in the oxidative reaction; both NAD(+) and NADP(+) were accepted as co-factors. Kinetic parameters for the oxidative and reductive reactions are consistent with a ternary complex mechanism.

Bacillus↗
PubMed2003

Identification of a mitochondrial glycerol-3-phosphate dehydrogenase from Arabidopsis thaliana: evidence for a mitochondrial glycerol-3-phosphate shuttle in plants.

We report molecular characterization of an Arabidopsis gene encoding a mitochondrial FAD-dependent glycerol-3-phosphate dehydrogenase (FAD-GPDH) that oxidizes glycerol-3-phosphate (G-3-P) to dihydroxyacetone phosphate. We demonstrate through in vitro targeting assays that the encoded gene product can be imported into mitochondrial membrane systems. Enzyme activity of the protein was confirmed through heterologous expression in Escherichia coli. The Arabidopsis gene is expressed throughout plant development, but at the highest level during seed germination. We also show that expression of the Arabidopsis FAD-GPDH gene is coupled to oxygen consumption and affected by ABA and stress conditions. Together with an NAD(+)-dependent GPDH, this enzyme could form a G-3-P shuttle, as previously established in other eukaryotic organisms, and links cytosolic G-3-P metabolism to carbon source utilization and energy metabolism in plants.

Amino Acid Sequence↗
PubMed2001

Improved determination of tributyl phosphate degradation products (mono- and dibutyl phosphates) by ion chromatography.

Tributyl phosphate (TBP) is a very important compound in the nuclear industry, particularly in the area of nuclear fuel reprocessing. This compound is used in the PUREX (plutonium and uranium refining extraction) process which consists of the extraction of uranium and plutonium from an aqueous nitric acid phase, for the purpose of recycling. But TBP may be degraded to dibutyl phosphate (DBP) and monobutyl phosphate (MBP) by dealkylation of one or two butoxy groups, respectively. We have compared and evaluated the capacity of two resins manufactured by Dionex (AS11 and AS5A) in the separation and measurement of these two degradation products. AS11 generates two interferences: nitrite/DBP and carbonate/MBP. The first one is the most serious. So, we have developed a method for oxidising nitrite ions to nitrate ions which have no trouble over the measurement. The second resin tested, AS5A, allows a very efficient separation between DBP and NO2- ions and a good separation between MBP and CO3(2-) in comparison with the AS11. The detection limits for the AS5A column are 0.13 microM for MBP and 0.71 microM for DBP (injection loop=50 microl).

Calibration↗
PubMed2001

Development of a microporous membrane liquid-liquid extractor for organophosphate esters in human blood plasma: identification of triphenyl phosphate and octyl diphenyl phosphate in donor plasma.

An extractor has been developed for microporous membrane liquid-liquid extraction (MMLLE) of lipophilic xenobiotics at trace levels in biological fluids. This new construction allows the sample phase to be stirred, while the organic phase is pumped. The extractor was evaluated using human blood plasma with added organophosphate esters. The size exclusion properties of the membrane reduced lipid co-extraction by approximately 94% compared to ordinary liquid-liquid extraction. In combination with a solid-phase extraction (SPE) step, the method was shown to remove plasma lipids efficiently and thus allow gas chromatographic separation of the compounds. The clean-up method described, including the SPE step, showed a high level of reproducibility, and recoveries of between 72 and 83% were obtained for five of the organophosphate esters after a 200-min extraction period. Using this technique, triphenyl phosphate and an isomer of octyl diphenyl phosphate were detected in human plasma obtained from blood donors. The concentration of triphenyl phosphate ranged between 0.13 and 0.15 microg/g plasma.

Blood Donors↗