Hydrolysis Of Tripolyphosphate Research Articles

Mechanism of Polyphosphates Hydrolysis by Purified Polyphosphatases from the Dorsal Muscle of Silver Carp (Hypophthalmichthys Molitrix) as Detected by ³¹P NMR.

The dynamic hydrolysis of tetrasodium pyrophosphate (TSPP), sodium tripolyphosphate (STPP) and polyphosphate compound, which was catalyzed by purified pyrophosphatase (PPase) and myosin- tripolyphosphatase (TPPase) from the silver carp dorsal muscle, was studied using (31) P NMR spectroscopy. In the PPase + TSPP system, the pyrophosphate (PP) was hydrolyzed quickly and completely within 8 h and the hydrolysis rate of PP was 12.51%/h. In the TPPase + STPP system, the first-order hydrolysis of tripolyphosphate (TPP) was not yet complete after 48 h, and the derived PP accumulated progressively. Given the coexistence of PPase and TPPase, only 1.20% of TPP in STPP alone remained after 48 h. However, the generation rate of Pi in the polyphosphate compound (TSPP: STPP: sodium hexametaphosphate = 1: 8: 1) was 0.76%/h, which was less than 0.88%/h in STPP alone. In the presence of polyphosphatases, the decrease of PP or TPP content in the polyphosphate compound was not as rapid as that in TSPP or STPP alone due to the inhibitory effect of PP on TPPase and the effect of low system pH on PPase. The understanding of polyphosphates hydrolysis mechanism was capable of developing the advanced polyphosphate mixture in order to reduce the phosphate residue in fish products. Processors appreciate the proven value of phosphates to increase the yield and functionality of the fish meat products. Our studies showed that the hydrolysis rate of PP or TPP in the blend was slower than that of polyphosphate alone. Thus, it is likely that the addition of PP and TPP in a polyphosphate blend had a prolonged interaction with proteins in fish meat processing and the effectiveness of polyphosphates was enhanced.

Purification and characterization of myosin-tripolyphosphatase from rabbit Psoas major muscle: Research note

In this study, we investigated the tripolyphosphatase (TPPase) activity responsible for the hydrolysis of tripolyphosphates (TPP) in rabbit Psoas major muscle tissue. After a series of extraction and purification steps, myosin was identified to be a TPPase. Optimum pH and temperature for myosin-TPPase activity were 6.0 and 35°C, respectively. We also found that myosin-TPPase activity was significantly influenced by Mg2+ and Ca2+ levels, whose optimal concentrations were determined to be 3 and 6mM, respectively. Furthermore, myosin-TPPase was strongly inhibited by EDTA-4Na+ and KIO3, and was slightly activated by EDTA-2Na+. These results suggest that it may be useful to regulate tripolyphosphate hydrolysis to enhance its function in meat processing.

Tripolyphosphate hydrolysis by bovine fast and slow myosin subfragment 1 isoforms

Polyphosphates are used in the meat industry to increase the water holding capacity of meat products. Tripolyphosphate (TPP) is a commonly used polyphosphate and it is metabolized into pyrophosphate and monophosphate in meat. The enzymes responsible for its metabolism have not been fully characterized. The motor domain of myosin (subfragment 1 or S1) is a likely candidate. The objectives of this study were to determine if bovine S1 hydrolyzes TPP, to characterize the TPPase activity of the fast (cutaneous trunci) and slow (masseter) isoforms, and to determine the influence of pH on S1 TPPase activity. S1 hydrolyzed TPP and in comparison with ATP as substrate, it hydrolyzed TPP 16-32% more slowly. Fast S1 hydrolyzed both substrates faster compared to slow S1 and the difference between the isoforms was greater with TPP as the substrate. The V(max) was 0.94 and 5.0 nmol Pi/mg S1 protein/min while the K(m) was 0.38 and 0.90 mM TPP for slow and fast S1, respectively. Pyrophosphate was a strong inhibitor of TPPase activity with a K(i) of 88 and 8.3 microM PPi for fast and slow S1 isoforms, respectively. Both ATPase and TPPase activities were influenced by pH with the activity being higher at low pH for both fast and slow S1 isoforms. The activity at pH 5.4 was 1.5 to 4-fold higher than that at pH 7.6 for the different isoforms and substrates. These data show that myosin S1 readily hydrolyzes TPP and suggest that it is a major TPPase in meat.

Colour tuning of core–shell fluorescent materials

Generally, two or more phosphors are mixed to achieve multiplex colour in the fluorescence industry. However, such a simple mixture of fluorescent materials usually leads to colour discrepancy and may even affect the colour uniformity due to the distinct physicochemical properties of the different components. Fabrication of a core–shell structure is a novel strategy to prepare colour-tuned fluorescent materials. Here we report a core–shell structure made up from two phosphors, Y2O3:Eu and LnPO4, which can emit red and green light respectively. It is important to control the homogeneous and relatively low supersaturation of LnPO4 (Ln = La, Ce, and Tb) in the solution so that the precipitates of LnPO4 can deposit onto the Y2O3:Eu particles uniformly. This could result in an LnPO4 shell around the Y2O3:Eu core to form micron-sized complex particles. In the preparation of the core–shell structure, the slow hydrolysis of tripolyphosphate to release free phosphate ions is a key factor. It is well known that dissociation of tripolyphosphate is temperature sensitive so that this reaction can be controlled by heating the solution. Under UV excitation, both the core (Y2O3:Eu) and the newly formed shell (LnPO4) can emit their characteristic light; it is interesting that each individual core–shell complex can provide the multiplex colour homogeneously at the micron scale. By adjusting the proportion of core and shell in the complex, the fluorescence colours of the micron-sized phosphor can be tuned conveniently.

Kinetic and Mutational Analyses of the Major Cytosolic Exopolyphosphatase from Saccharomyces cerevisiae

Yeast exopolyphosphatase (scPPX) processively splits off the terminal phosphate group from linear polyphosphates longer than pyrophosphate. scPPX belongs to the DHH phosphoesterase superfamily and is evolutionarily close to the well characterized family II pyrophosphatase (PPase). Here, we used steady-state kinetic and binding measurements to elucidate the metal cofactor requirement for scPPX catalysis over the pH range 4.2-9.5. A single tight binding site for Mg(2+) (K(d) of 24 microm) was detected by equilibrium dialysis. Steady-state kinetic analysis of tripolyphosphate hydrolysis revealed a second site that binds Mg(2+) in the millimolar range and modulates substrate binding. This step requires two protonated and two deprotonated enzyme groups with pK(a) values of 5.0-5.3 and 7.6-8.2, respectively. The catalytic step requiring two deprotonated groups (pK(a) of 4.6 and 5.6) is modulated by ionization of a third group (pK(a) of 8.7). Conservative mutations of Asp(127), His(148), His(149) (conserved in scPPX and PPase), and Asn(35) (His in PPase) reduced activity by a factor of 600-5000. N35H and D127E substitutions reduced the Mg(2+) affinity of the tight binding site by 25-60-fold. Contrary to expectations, the N35H variant was unable to hydrolyze pyrophosphate, but markedly altered metal cofactor specificity, displaying higher catalytic activity with Co(2+) bound to the weak binding site versus the Mg(2+)- or Mn(2+)-bound enzyme. These results provide an initial step toward understanding the dynamics of scPPX catalysis and reveal significant functional differences between structurally similar scPPX and family II PPase.

Mutational analysis of methionine adenosyltransferase from Leishmania donovani.

The methionine adenosyltransferase (MAT; EC 2.5.1.6) mediated synthesis of S-adenosylmethionine (AdoMet) is a two-step process, consisting of the formation of AdoMet and the subsequent cleavage of the tripolyphosphate (PPPi) molecule, a reaction induced, in turn, by AdoMet. The fact that the two activities--AdoMet synthesis and tripolyphosphate hydrolysis--can be measured separately is particularly useful when the site-directed mutagenesis approach is used to determine the functional role of the amino acid residues involved in each. This report describes the mutational analysis of the amino acids involved in both the ATP and L-methionine binding sites of Leishmania donovani MAT (GenBank accession number AF179714) the aetiological agent of visceral leishmaniasis. Site-directed mutagenesis was used to substitute neutral residues for the basic amino acid (Lys168, Lys256, Lys276, Lys280 and His17), acidic residues (Asp19, Asp121, Asp166, Asp249, Asp277 and Asp288) and Phe241 involved in AdoMet synthesis and PPPi hydrolysis. With the exception of D116N, none of these mutants was able to synthesize AdoMet at a significant rate, although H17A, H17N, K256A, K280A, D19N, D121N, D166N, D249N and D282N showed measurable tripolyphosphatase activity. Finally, the C-terminus domain of L. donovani MAT was truncated at three points (F382Stop, D375Stop, F368Stop), deleting a 3(10) one-turn helix motif in all three cases. Whilst none of the truncated proteins conserved MAT activity, they were able to hydrolyse PPPi, albeit at a lower rate than the wild-type enzyme. A fourth protein with an internal deletion (E376DeltaF382) in the C-terminal domain conserved high tripolyphosphatase activity, which was not, however, induced by 50 microM AdoMet.

Leishmania donovani methionine adenosyltransferase. Role of cysteine residues in the recombinant enzyme.

Methionine adenosyltransferase (MAT, EC 2.5.1.6)-mediated synthesis of S-adenosylmethionine (AdoMet) is a two-step process consisting of the formation of AdoMet and the subsequent cleavage of the tripolyphosphate (PPPi) molecule, a reaction induced, in turn, by AdoMet. The fact that the two activities, AdoMet synthesis and tripolyphosphate hydrolysis, can be measured separately is particularly useful when the site-directed mutagenesis approach is used to determine the functional role of the amino acid residues involved in each. The present report describes the cloning and subsequent functional refolding, using a bacterial expression system, of the MAT gene (GenBank accession number AF179714) from Leishmania donovani, the etiological agent of visceral leishmaniasis. The absolute need to include a sulfhydryl-protection reagent in the refolding buffer for this protein, in conjunction with the rapid inactivation of the functionally refolded protein by N-ethylmaleimide, suggests the presence of crucial cysteine residues in the primary structure of the MAT protein. The seven cysteines in L. donovani MAT were mutated to their isosterical amino acid, serine. The C22S, C44S, C92S and C305S mutants showed a drastic loss of AdoMet synthesis activity compared to the wild type, and the C33S and C47S mutants retained a mere 12% of wild-type MAT activity. C106S mutant activity and kinetics remained unchanged with respect to the wild-type. Cysteine substitutions also modified PPPi cleavage and AdoMet induction. The C22S, C44S and C305S mutants lacked in tripolyphosphatase activity altogether, whereas C33S, C47S and C92S retained low but detectable activity. The behavior of the C92S mutant was notable: its inability to synthesize AdoMet combined with its retention of tripolyphosphatase activity appear to be indicative of the specific involvement of the respective residue in the first step of the MAT reaction.

Abiotic hydrolysis of the detergent builder tripolyphosphate by hydrous manganese dioxide

The hydrolysis of tripolyphosphate to orthophosphate is facilitated by suspensions of amorphous manganese dioxide. Pyrophosphate is observed as an intermediate. The rate enhancement decreases with increasing pH. The weak sorption of orthophosphate on the oxide also decreases with increasing pH, indicating that the orthophosphate product would be bioavailable. The presence of calcium ions in natural waters increases both the rate of hydrolysis of tripolyphosphate and the extent of sorption of orthophosphate. Under some circumstances this abiotic mechanism could play a significant role in the hydrolysis of tripolyphosphate in the aquatic environment.

The crystal structure of tetrameric methionine adenosyltransferase from rat liver reveals the methionine-binding site

Most of the transmethylation reactions use the same methyl donor, S-adenosylmethionine (SAM), that is synthesised from methionine and ATP by methionine adenosyltransferase (MAT). In mammals, two MAT enzymes have been detected, one ubiquitous and another liver specific. The liver enzyme exists in two oligomeric forms, a tetramer (MAT I) and a dimer (MAT III), MAT I being the one that shows a higher level of affinity for methionine but a lower SAM synthesis capacity. We have solved the crystal structure of rat liver MAT I at 2.7 Å resolution, complexed with a methionine analogue: l-2-amino-4-methoxy-cis-but-3-enoic acid (l-cisAMB). The enzyme consists of four identical subunits arranged in two tight dimers that are related by crystallographic 2-fold symmetry. The crystal structure shows the positions of the relevant cysteine residues in the chain, and that Cys35 and Cys61 are perfectly oriented for forming a disulphide link. This result leads us to propose a hypothesis to explain the control of MAT I/III exchange and hence, the effects observed on activity. We have identified the methionine-binding site into the active-site cavity, for the first time. The l-cisAMB inhibitor is stacked against Phe251 aromatic ring in a rather planar conformation, and its carboxylate group coordinates a Mg2+, which, in turn, is linked to Asp180. The essential role of the involved residues in MAT activity has been confirmed by site-directed mutagenesis. Phe251 is exposed to solvent and is located in the beginning of the flexible loop Phe251-Ala260 that is connecting the N-terminal domain to the central domain. We postulate that a conformational change may take place during the enzymatic reaction and this is possibly the reason of the unusual two-step mechanism involving tripolyphosphate hydrolysis. Other important mechanistic implications are discussed on the light of the results. Moreover, the critical role that certain residues identified in this study may have in methionine recognition opens further possibilities for rational drug design.

Solid-State Hydrolysis of Calcium Tripolyphosphate Scales

Precipitation of calcium tripolyphosphate (CaTPP) from strongly supersaturated solution is accompanied by tripolyphosphate hydrolysis if the bulk Ca/TPP mole ratio is in excess of about 2. Along with the tendency for hydrolysis, a change in the crystal habit from crystalline to amorphous is observed beyond this bulk ratio. The composition of the material changes as well from mainly Ca2NaP3O10 at a 2:1 Ca/TPP bulk ratio to Ca5(P3O10)2 at an 8:1 bulk ratio, though the water of hydration contents are similar. The crystallinity change is reflected in the IR and solid-state 31P NMR spectra, but, beyond these expected differences, the amorphous samples also appear to have a larger fraction of more mobile crystal water. Through a series of sequential experiments, it was identified that hydrolysis of these materials mainly occurs via a mechanism consisting of precipitation of CaTPP followed by hydrolysis of the precipitate. Bulk water does not play a critical role in the hydrolysis nor does surface adsorbed water...

The Bifunctional Active Site of S-Adenosylmethionine Synthetase: ROLES OF THE BASIC RESIDUES

S-adenosylmethionine (AdoMet) synthetase catalyzes a unique two-step enzymatic reaction leading to formation of the primary biological alkylating agent. The crystal structure of Escherichia coli AdoMet synthetase shows that the active site, which lies between two subunits, contains four lysines and one histidine as basic residues. In order to test the proposed charge and hydrogen bonding roles in catalytic function, each lysine has been changed to an uncharged methionine or alanine, and the histidine has been altered to asparagine. The resultant enzyme variants are all tetramers like the wild type enzyme; however, circular dichroism spectra show reductions in helix content for the K245*M and K269M mutants. (The asterisk denotes that the residue is in the second subunit.) Four mutants have k(cat) reductions of approximately 10(3)-10(4)-fold in AdoMet synthesis; however, the k(cat) of K165*M variant is only reduced 2-fold. In each mutant, there is a smaller catalytic impairment in the partial reaction of tripolyphosphate hydrolysis. The K165*A enzyme has a 100-fold greater k(cat) for tripolyphosphate hydrolysis than the wild type enzyme, but this mutant is not activated by AdoMet in contrast to the wild type enzyme. The properties of these mutants require reassessment of the catalytic roles of these residues.

Adenosine 5'-tetraphosphate phosphohydrolase from yellow lupin seeds: purification to homogeneity and some properties.

Adenosine 5'-tetraphosphate phosphohydrolase (EC 3.6.1.14) has been purified to homogeneity from the meal of yellow lupin (Lupinus luteus) seeds. The enzyme is a single polypeptide chain of 25+/-1 kDa. It catalyses the hydrolysis of a nucleoside 5'-tetraphosphate to a nucleoside triphosphate and orthophosphate, and hydrolysis of tripolyphosphate but neither pyrophosphate nor tetraphosphate. A divalent cation, Mg2+, Co2+, Ni2+ or Mn2+, is required for these reactions. The pH optimum for hydrolysis of adenosine 5'-tetraphosphate (p4A) is 8.2, Vmax is 21+/-1.7 micromol/min per mg of protein and the Km for p4A is 3+/-0.6 microM. At saturating p4A concentrations, the rate constant for the reaction is 8.5+/-0.7 s-1 [at 30 degrees C, in 50 mM Hepes/KOH (pH8.2)/5 mM MgCl2/0.1 mM dithiothreitol]. p4A and guanosine 5'-tetraphosphate are hydrolysed at the same rate. Adenosine 5'-pentaphosphate (p5A) is degraded 1/200 as fast and is converted into ATP and two molecules of orthophosphate, which are liberated sequentially. This contrasts with the cleavage of p5A by the lupin diadenosine tetraphosphate hydrolase (EC 3.6.1.17), which gives ATP and pyrophosphate. Zn2+, F- and Ca2+ ions inhibit the hydrolysis of p4A with I50 values of 0.1, 0.12 and 0.2 mM respectively.

Structure and function of S-adenosylmethionine synthetase: crystal structures of S-adenosylmethionine synthetase with ADP, BrADP, and PPi at 28 angstroms resolution.

S-Adenosylmethionine synthetase (MAT,ATP:L-methionine S-adenosltransferase, EC 2.5.1.6) plays a central metabolic role in all organisms. MAT catalyzes the two-step reaction which synthesizes S-adenosylmethionine (AdoMet), pyrophosphate (PPi), and orthophosphate (Pi) from ATP and L-methionine. AdoMet is the primary methyl group donor in biological systems. The first crystal structure of MAT from Escherichia coli has recently been determined [Takusagawa et al. (1995) J. Biol. Chem. 271, 136-147]. In order to elucidate the active site and possible catalytic reaction mechanism, the MAT structures in the crystals grown with the substrate ATP (and BrATP) and the product PPi have been determined (space group P6(2)22; unit cell a = b = 128.9 Angstroms, c= 139.8 Angstroms, resolution limit 2.8 Angstroms; R O.19; Rfree 0.26). The enzyme consists of four identical subunits; two subunits form a spherical dimer, and pairs of these tightly bound dimers form a tetrameric enzyme. Each dimer has two active sites which are located between the subunits. Each subunit consists of three domains related to each other by a pseudo 3-fold symmetry. The crystal structures showed that the ATP molecules were hydrolyzed to ADP and Pi by the enzyme. Those products were found at the active site along with the essential metal ions (K+ and Mg2+). This rather unexpected finding was first confirmed by the structure of the complex with PPi and later by an HPLC analysis. The enzyme hydrolyzed ATP to ADP and Pi in 72 h under the same conditions as the crystallization of the enzyme. In the active site, the diphosphate moiety of ADP and Pi interacts extensively with amino acid residues from the two subunits of the enzyme, whereas the adenine and ribose moieties have little interaction with the enzyme. The enzyme structure is little changed upon binding ADP. All amino acid residues involved in the active site are found to be conserved in the 14 reported sequences of MAT from a wide range of organisms. Thus the structure determined in this study can be utilized as a model for other members of the MAT family. On the basis of the crystal structures, the catalytic reaction mechanisms of AdoMet formation and hydrolysis of tripolyphosphate are proposed.

Investigation of Monovalent Cation Activation of S-Adenosylmethionine Synthetase Using Mutagenesis and Uranyl Inhibition

S-Adenosylmethionine (AdoMet) synthetase catalyzes the formation of AdoMet from ATP and L-methionine with subsequent hydrolysis of the bound tripolyphosphate intermediate. Maximal activity requires the presence of two divalent and one monovalent cation per active site. Recently, the x-ray structure of the Escherichia coli AdoMet synthetase was solved, and the positions of the two Mg2+ binding sites were identified. Based on additional spherical electron density, the K+ binding site was postulated to be a nearby site where the uranyl heavy atom derivative also bound in the crystal. The side chain of glutamate 42 is within ligation distance of the metals. Mutagenesis of glutamate 42 to glutamine (E42QMetK) abolished monovalent cation activation and produced an enzyme that has kinetic properties virtually identical to those of K(+)-free wild type AdoMet synthetase in both the overall AdoMet synthetase reaction and in the hydrolysis of tripolyphosphate. Thus, there is a approximately 100-fold decrease in the Vmax for AdoMet synthesis and large increases in the Km values for both substrates. In contrast there is only a 2-fold decrease in Vmax for tripolyphosphate hydrolysis. The uranyl ion, UO2(2+), is a competitive inhibitor with respect to K+ (Ki = 350 nM) and is the first ion to bind at this site and inhibit the enzyme. The UO2(2+) inhibition is reversible and tight-binding, and results from UO2(2+) and not UO2(2+)-ATP. Analogous to K+ activation, UO2(2+) predominantly inhibits AdoMet formation rather than tripolyphosphate hydrolysis. The kinetic results indicate that UO2(2+) inhibition is likely to result from interference with productive ATP binding. UO2(2+) remains a tight-binding inhibitor of the E42Q mutant, which suggests that K+ and UO2(2+) have different ligation preferences when bound in the monovalent cation binding pocket. The results support the model that glutamate 42 provides ligands to the K+ and has a major role in monovalent cation binding.

31P N.m.r. studies of the hydrolysis of added phosphates in chicken meat

AbstractThe hydrolysis of tripolyphosphate and pyrophosphate in comminuted chicken muscle was examined quantitatively by 31P n.m.r. Ageing the muscle before addition of phosphates resulted in a similar change of the hydrolysis rate of both species. By contrast addition of sodium chloride caused very rapid hydrolysis of tripolyphosphate and slowing of the hydrolysis of pyrophosphate. Untreated muscle showed very low levels of phosphocreatine immediately after death and complete loss of ATP within one hour.

FACTOR INTERACTIONS AND THEIR INFLUENCE ON HYDROLYSIS OF CONDENSED PHOSPHATES IN SOILS1

In a laboratory study, we determined the main and first-order interactive effects of soil moisture, organic matter content, temperature, pH, texture, and incubation time on hydrolysis of pyrophosphate and tripo-lyphosphate. We used six diverse soils from Texas that were classified as entisols, alfisols, or vertisols and ranged in pH from 4.3 to 7.9, in organic matter contents from 0.8 to 4.9%, and in texture from loams to clay. Significant main effects for pyrophosphate hydrolysis were soil texture, pH, moisture content, temperature, and time; tripolyphosphate hydrolysis was affected only by soil pH, temperature, and time. The main effects did not represent statistically valid indications of the importance of these parameters on hydrolysis, however, because these factors were also involved in significant interactions. Significant interactions for pyrophosphate hydrolysis were texture x organic matter content, texture x pH, texture x time, organic matter x time, pH x soil moisture, pH x time, and temperature x time. Texture x moisture, pH x moisture, pH x time, moisture x time, and temperature x time were interactions that significantly altered hydrolysis of tripolyphosphate. The presence of interactions demonstrated that the studied parameters were not independent and confirmed the intricacy of poly-phosphate hydrolysis reactions. Significant interactions were delineated into component factors to determine the nature of each interaction and its influence on hydrolysis.

EFFECTS OF TEMPERATURE AND PHOSPHATE CONCENTRATION ON RATE OF SODIUM PYROPHOSPHATE AND SODIUM TRIPOLYPHOSPHATE HYDROLYSIS IN SOIL

Rates of hydrolysis of water-soluble sodium pyrophosphate and sodium tripolyphosphate, applied to soil at 200 ppm P, were extremely rapid (about 2–7%/h) during the 0 to 24- or 0- to 48-h period following phosphate application but decreased with time of incubation. Rates of hydrolysis increased linearly and increased about two- to threefold as temperatures were increased from 5 to 35 C or from 5 to 50 C. Inconsistent results were obtained at temperatures above 50 C. Increases in incubation temperature increased the total amount of added polyphosphate hydrolyzed by the soil in 120 h from about 40 to 70% at 5 C to about 80 to 95% at 35 C and 50 C. Water-soluble polyphosphate hydrolyzed at a greater rate than 0.5 N H2SO4-soluble polyphosphate. However, the effects of temperature on rate of hydrolysis of acid-soluble polyphosphate and water-soluble polyphosphate were similar. Polyphosphate hydrolyzed at a greater rate in the noncalcareous Newdale soil than in the calcareous Lakeland soil. Rate of tripolyphosphate hydrolysis was usually greater than rate of pyrophosphate hydrolysis. Rate of hydrolysis of water-soluble polyphosphate, expressed as %/h, decreased exponentially as concentration of applied polyphosphate increased from 200 to 1,600 ppm. However, rate of orthophosphate production per unit time increased exponentially with increased substrate concentration.

Kinetics of Pyro‐ and Tripolyphosphate Hydrolyses in the Presence of Corn and Soybean Roots as Determined by NMR Spectroscopy

AbstractKinetics of pyro‐ and tripolyphosphate hydrolyses by corn (Zea mays L. var. ‘NK P × 50 A’) and soybean (Glycine max L. Merv. var. ‘Cutler 71’) roots were studied using a split‐root technique to supply nutrients and to prevent precipitation reactions between phosphate sources and other nutrients. Phosphate species were determined by nuclear magnetic resonance (NMR) spectroscopy after freeze drying to concentrate the sample. A chelating agent eliminated interference by ions in sample solutions.Hydrolyses of pyro‐ and tripolyphosphates at substrate concentrations of 75 ppm P followed zero‐order kinetics. Pyro‐ and tripolyphosphates were hydrolyzed faster by corn roots than by soybean roots under the conditions studied. The zero‐order rate constant for hydrolysis of pyrophosphate was 4.36 × 10−2 mmoles hour−1 in the presence of corn roots and 1.38 × 10−2 mmoles hour−1 in the presence of soybean roots. During tripolyphosphate hydrolyses by corn and soybean roots, tripolyphosphate concentration decreased linearly and orthophosphate concentration increased linearly; pyrophosphate hydrolyzed faster than tripolyphosphate. Rate constants for hydrolysis of tripolyphosphate were 2.50 × 10−2 mmoles hour−1 and 5.42 × 10−3 mmoles hour−1 by corn and soybean roots, respectively.

Tripolyphosphate and Pyrophosphate Hydrolysis in Sediments

AbstractThe rate of hydrolysis of tripolyphosphate (TPP) and pyrophosphate (PP) in river, creek, and lake sediments was determined. Half‐lives for the hydrolysis of TPP and PP ranged from 1.6 to 2.6 and 6.7 to 27.4 days, respectively. The influence of temperature, biological activity, and pH on the rate of TPP and PP hydrolysis was investigated using Flat Branch Creek sediment. The rate of TPP and PP hydrolysis increased with increasing temperature. The activation energy was 5,415 cal/mole for TPP and 10,412 cal/mole for PP. TPP and PP hydrolyzed slower in sediment which had been autoclaved than in non‐sterilized sediment. The half‐life for TPP hydrolysis was 1.76 day at pH 5, 1.61 day at pH 7, and 2.16 day at pH 9. The rate of PP hydrolysis was increased as pH increased from 5 to 7 to 9 as indicated by half‐lives of 13.7, 10.0, and 7.3 days, respectively. When TPP was added to the sediment as a Ca5(P3O10)2 precipitate, the rate of hydrolysis was slower than when TPP was added as a solution.

The Mechanism of the Hydrolysis of Condensed Phosphates. III. The Mechanism of the Hydrolysis of Trimeta- and Tetrametaphosphates

Abstract The hydrolysis of sodium trimeta- and tetrametaphosphates was run in water, dioxane–water, and formic acid–water solvents with an initial concentration of 0.025 mol/l at various pH values and temperatures. The hydrolysis of both the metaphosphates followed first-order kinetics with respect to the concentration of the phosphate under all the conditions studied and was an acid- and base-catalyzed reaction. In acidic solutions, the rate of hydrolysis of both the metaphosphates in water is faster than that in formic acid–water and slower than that in dioxane-water. Therefore, it is concluded that, in the formic acid–water solvent, the nucleophilicity of the water molecule may decrease on account of the solvation of the water molecule with the acid, while, in the dioxane–water solvent, since the scission of the hydrogen bond between water molecules may occur by the interaction of dioxane and water molecules, the nucleophilicity of the water molecule may increase. The hydrolysis of both metaphosphates in acidic solutions is considered to be an SN2 reaction, because the overall-reaction rate is highly dependent upon the nucleophilicity of the water molecule. In basic solutions, the rate of hydrolysis of sodium trimeta- and tetrametaphosphates in water is faster than or almost the same as that in dioxane-water. Consequently, the mechanism of the hydrolysis of both the metaphosphates in basic solutions seems to differ from that in acidic solutions. The increase in the rate of hydrolysis of small-ring phosphates in acidic solutions depends upon the activation energy and frequency factor, while that in basic solutions depends significantly upon the frequency factor. This may cause the difference in the solvent effect on the rate of hydrolysis of small-ring phosphates between acidic and basic solutions. The activation energy of the hydrolysis of both ring phosphates was 20–40 kcal/mol in the pH range of 1.0–12.5. The rate of hydrolysis of the metaphosphates in an aqueous sodium hydroxide solution is faster than that in an aqueous tetramethyl ammonium hydroxide solution and this can be attributed to catalysis by a sodium ion. The hydrolysis of sodium tripolyphosphate was also carried out in basic water and dioxane–water solvents. The solvent effect on the rate of hydrolysis of tripolyphosphate in basic solutions was the same as that in acidic solutions.