scholarly journals Hydrolysis of Adenosine Triphosphate by Crystalline Yeast Pyrophosphatase

1962 ◽  
Vol 45 (4) ◽  
pp. 31-46 ◽  
Author(s):  
M. Kunitz
Keyword(s):  
Ion Exchange ◽  
Protein Molecule ◽  
Molar Ratio ◽  
Inorganic Pyrophosphatase ◽  
Inorganic Pyrophosphate ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Zn Ions ◽  
Dowex 1

Schlesinger and Coon's report that crystalline yeast inorganic pyrophosphatase, in addition to its known ability to hydrolyze inorganic pyrophosphate in the presence of Mg ions, is also able to catalyze the hydrolysis of ATP and ADP in the presence of Zn ions was confirmed. A systematic study showed that the ratio of 370 of PPase-Mg over ATPase-Zn activities per milligram protein in various preparations of pyrophosphatase obtained in the course of isolation of crystalline pyrophosphatase from baker's yeast was nearly identical in all the preparations, independent of their purity. The course of hydrolysis of ATP by crystalline pyrophosphatase in the presence of Zn was carried out with the aid of ion exchange on Dowex 1. The finding of Schlesinger and Coon that the hydrolysis proceeds from ATP to ADP and then slowly to AMP was confirmed. The kinetics of the first phase of the reaction was found to depend on the molar ratio of Zn/ATP in the reaction mixture. Mg ions in the presence of Zn ions have an accelerating effect on the rate of hydrolysis of ATP. This suggests strongly that both activities—ATPase and PPase—are manifestations of the same active group in the protein molecule of crystalline pyrophosphatase.

Kinetics of hydrolysis of peroxodisulphate ions in acidic medium to peroxomonosulphuric acid

1981 ◽  
Vol 46 (5) ◽  
pp. 1229-1236 ◽  
Author(s):  
Jan Balej ◽  
Milada Thumová
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Acidic Medium ◽  
Measured Data ◽  
Molar Ratios ◽  
Starting Solution ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of

The rate of hydrolysis of S2O82- ions in acidic medium to peroxomonosulphuric acid was measured at 20 and 30 °C. The composition of the starting solution corresponded to the anolyte flowing out from an electrolyser for production of this acid or its ammonium salt at various degrees of conversion and starting molar ratios of sulphuric acid to ammonium sulphate. The measured data served to calculate the rate constants at both temperatures on the basis of the earlier proposed mechanism of the hydrolysis, and their dependence on the ionic strength was studied.

scholarly journals Chicken Intestinal Alkaline Phosphatase

1960 ◽  
Vol 43 (6) ◽  
pp. 1149-1169 ◽  
Author(s):  
M. Kunitz
Keyword(s):  
Alkaline Phosphatase ◽  
Zinc Ions ◽  
Magnesium Ions ◽  
Intestinal Alkaline Phosphatase ◽  
Reversible Inactivation ◽  
Higher Temperature ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Zn Ions ◽  
Denaturation Of Proteins

Purified chicken intestinal alkaline phosphatase is active at pH 8 to 9, but becomes rapidly inactivated with change of pH to 6 or less. Also, a solution of the inactivated enzyme at pH 4.5 rapidly regains its activity at pH 8. In the range of pH 6 to 8 a solution of purified alkaline phosphatase consists of a mixture of active and inactive enzyme in equilibrium with each other. The rate of inactivation at lower pH and of reactivation at higher pH increases with increase in temperature. Also, the activity at equilibrium in the range of pH 6 to 8 increases with temperature so that a solution equilibrated at higher temperature loses part of its activity on cooling, and vice versa, a rise in temperature shifts the equilibrium toward higher activity. The kinetics of inactivation of the enzyme at lower pH and the reactivation at higher pH is that of a unimolecular reaction. The thermodynamic values for the heat and entropy of the reversible inactivation and reactivation of the enzyme are considerably lower than those observed for the reversible denaturation of proteins. The inactivated enzyme at pH 4 to 6 is rapidly reactivated on addition of Zn ions even at pH 4 to 6. However, zinc ions are unable to replace magnesium ions as cocatalysts for the enzymatic hydrolysis of organic phosphates by alkaline phosphatase.

scholarly journals Mechanism of IPPase shown by high resolution Neutron and X-ray crystallography

2014 ◽  
Vol 70 (a1) ◽  
pp. C1211-C1211
Author(s):  
Joseph Ng ◽  
Ronny Hughes ◽  
Michelle Morris ◽  
Leighton Coates ◽  
Matthew Blakeley ◽  
...  
Keyword(s):  
High Resolution ◽  
Active Site ◽  
Inorganic Pyrophosphatase ◽  
Inorganic Pyrophosphate ◽  
X Ray ◽  
X Ray Crystallography ◽  
Cellular Processes ◽  
Crystallographic Structures ◽  
Hydrolysis Of ◽  
Low Energy Conformations

Soluble inorganic pyrophosphatase (IPPase) catalyzes the hydrolysis of inorganic pyrophosphate (PPi) to form orthophosphate (Pi). The action of this enzyme shifts the overall equilibrium in favor of synthesis during a number of ATP-dependent cellular processes such as in the polymerization of nucleic acids, production of coenzymes and proteins and sulfate assimilation pathways. Two Neutron crystallographic (2.10-2.50Å) and five high-resolution X-ray (0.99Å-1.92Å) structures of the archaeal IPPase from Thermococcus thioreducens have been determined under both cryo and room temperatures. The structures determined include the recombinant IPPase bound to Mg+2, Ca+2, Br-, SO2-2 or PO4-2 involving those with non-hydrolyzed and hydrolyzed pyrophosphate complexes. All the crystallographic structures provide snapshots of the active site corresponding to different stages of the hydrolysis of inorganic pyrophosphate. As a result, a structure-based model of IPPase catalysis is devised showing the enzyme's low-energy conformations, hydration states, movements and nucleophile generation within the active site.

STRUCTURE OF A GALACTURONAN FROM SUNFLOWER PECTIC ACID

1966 ◽  
Vol 44 (11) ◽  
pp. 1275-1282 ◽  
Author(s):  
V. Zitko ◽  
C. T. Bishop
Keyword(s):  
Galacturonic Acid ◽  
Periodate Oxidation ◽  
Degree Of Polymerization ◽  
Critical Assessment ◽  
Molar Ratio ◽  
Aqueous Methanol ◽  
Pectic Acid ◽  
Potassium Borohydride ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Fractions of sunflower pectic acid containing 89.8%, 94.2%, and 91.4% of D-galacturonic acid were carboxyl reduced as their methyl or ethylene glycol esters by potassium borohydride. Critical assessment of the effects of three different solvents (water, 80% aqueous dimethyl sulfoxide, and 80% aqueous methanol) on the efficiency of reduction showed that the latter solvent was best. The reductions caused a decrease in the degree of polymerization from 270 to 21. Measurement of the rates of hydrolysis of partially reduced pectic acids containing 90%, 41.6%, 19.9%, 11.0%, and 0.65% of D-galacturonic acid showed that the rate of hydrolysis was directly related to the proportion of galacturonosidic linkages present. Methylation and hydrolysis of the carboxyl-reduced pectic acid fractions yielded 2,3,4,6-tetra-O-methyl-D-galactose and 2,3,6-tri-O-methyl-D-galactose in an approximate molar ratio of 1:20. Results of the periodate oxidation of the carboxyl-reduced pectic acid supported the conclusion inferred from the methylation results that the pectic acid was a linear polymer of 1 → 4 linked α-D-galacturonic acid units.

Study and modeling of mechanisms of cholinesterasis reactions in order to improve their catalytic properties in the neutralization reactions of organophosphorous compounds

2020 ◽  
pp. 134-174
Author(s):  
Sergey Varfolomeev ◽  
Bella Grigorenko ◽  
Sofya Lushchekina ◽  
Patrick Masson ◽  
Galina Mahaeva ◽  
...  
Keyword(s):  
First Generation ◽  
Organophosphorus Compounds ◽  
Protein Molecule ◽  
Catalytic Antibodies ◽  
High Rate ◽  
Biological Targets ◽  
Organophosphorous Compounds ◽  
Rate Of Hydrolysis ◽  
The Stability ◽  
Hydrolysis Of

“Biocleaners” or “bioscavengers” are biological objects (enzymes, catalytic antibodies) that are capable of binding and/or hydrolyzing organophosphorus compounds (OPC). Their use seems to be the most effective alternative to traditional antidotes to neutralize or detoxify OPC. The introduction of bioscavengers allows neutralizing toxicant molecules in the bloodstream before they reach their biological targets, thereby providing protection against poisoning. Bioscavengers of the first-generation neutralized OPC molecules by stoichiometrically binding to them. The safety and efficacy of human butyrylcholinesterase (BChE) for protecting against OPC poisoning has been shown. However, the stoichiometric neutralization of OPC requires the introduction of a huge amount of expensive biopharmaceuticals. Catalytic bioscavengers that hydrolytically neutralize OPC were introduced at a much lower dose to achieve the same degree of effectiveness. The most effective catalytic bioscavengers are enzymes. The most promising enzymes are artificial mammalian paraoxonase mutants and bacterial phosphotriesterases. However, studies of other enzymes, such as prolidases, oxidases, artificial mutants of cholinesterases and carboxyl esterases and catalytic antibodies are actively ongoing. Since OPC are pseudosubstrates of cholinesterases (ChEs), a detailed description of the mechanisms of inhibition, dealkylation, and spontaneous reactivation of phosphorylated ChEs is critical for the development of ChEs mutants with a high rate of hydrolysis of OPC. The review presents an analysis of different views on the mechanisms of interaction of ChEs with OPC, discusses the possible directions of creating effective catalytic biological traps based on BChE and changes in their mechanism of action as compared to the native enzyme. A separate section is devoted to the effect of mutations, both polymorphic and artificial, on the stability of the protein molecule of BChE.

THE METABOLISM OF THE ERYTHROCYTE: X. THE INORGANIC PYROPHOSPHATASE OF THE ERYTHROCYTE

1956 ◽  
Vol 34 (1) ◽  
pp. 121-129 ◽  
Author(s):  
A. Malkin ◽  
O. F. Denstedt
Keyword(s):  
Enzyme Activity ◽  
Calcium Ions ◽  
Human Erythrocyte ◽  
Inorganic Pyrophosphatase ◽  
Magnesium Ions ◽  
Constant Ratio ◽  
Inorganic Pyrophosphate ◽  
Noncompetitive Inhibitor ◽  
Pyrophosphatase Activity ◽  
Hydrolysis Of

The activity of the pyrophosphatase which catalyzes the hydrolysis of inorganic pyrophosphate in the erythrocyte of the human, the rabbit, and the chicken is confined entirely to the cytoplasm of the cell. Following preincubation, the enzyme activity in the human erythrocyte is diminished, but pre-incubation in the presence of cysteine or glutathione prevents the diminution of the enzyme activity. Aging of the hemolyzate of the human erythrocytes results in a marked loss of the inorganic pyrophosphatase activity. The diminished activity can be restored by the addition of cysteine or glutathione to the reaction mixture; but after the hemolyzate has aged for five or six days at 5 °C, the loss in the enzyme activity can no longer be restored with these reagents. Fluoride and calcium ions inhibit the activity of the enzyme, while magnesium ions are essential for its activity. Calcium is a noncompetitive inhibitor, while the inhibition by fluoride is of a "quadratic" nature. If a constant ratio of magnesium to pyrophosphate is maintained, the quadratic inhibition can be converted to the "uncompetitive" type of inhibition.

scholarly journals Effects of spermine and spermidine on the inorganic pyrophosphatase of Streptococcus faecalis. Interactions between polyamines and inorganic pyrophosphate

1989 ◽  
Vol 259 (1) ◽  
pp. 55-59 ◽  
Author(s):  
R Lahti ◽  
R Hannukainen ◽  
H Lönnberg
Keyword(s):  
Gamma Ray ◽  
Inorganic Pyrophosphatase ◽  
Emission Analysis ◽  
Streptococcus Faecalis ◽  
Inorganic Pyrophosphate ◽  
Bivalent Cations ◽  
Hydrolysis Of ◽  
Apparent Stability ◽  
Allosteric Activator

We have shown a dual role for Mg2+ in the hydrolysis of PPi catalysed by inorganic pyrophosphatase (PPase; EC 3.6.1.1) of Streptococcus faecalis; Mg2+ is necessary for the formation of the substrates, Mg1PPi2- and Mg2PPi0, and it also acts as an allosteric activator [Lahti + Jokinen (1985) Biochemistry 24, 3526-3530]. No activity can be observed with S. faecalis PPase in the absence of bivalent cations, which indicates that free PPi cannot serve as a substrate for this enzyme. However, significant activities were observed in the presence of spermine and spermidine, even though no bivalent cations were present. It was shown by particle-induced gamma-ray emission and particle-induced X-ray-emission analysis that the polyamines used were not contaminated with Mg2+ or any other bivalent cations that could support PPase activity. Hence it is obvious that polyamines are able to form a complex with PPi that serves as a substrate for PPase. The apparent stability constants for the 1:1 adducts of spermine and spermidine were estimated by a resin competition method. The values obtained at pH 7.5 were 2.7 X 10(3) M-1 and 6.4 X 10(2) M-1 respectively. Kinetic results further suggested that polyamines can also substitute for Mg2+ as an activator in vitro. The physiological significance of these polyamine effects were discussed.

Mechanistic Information from the Effect of Pressure on the Kinetics of Hydrolysis of Iodopentaaquochromium(III) Ion

1975 ◽  
Vol 53 (24) ◽  
pp. 3697-3701 ◽  
Author(s):  
Milton Cornelius Weekes ◽  
Thomas Wilson Swaddle
Keyword(s):  
Ionic Strength ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Aqueous Hclo ◽  
Conjugate Base

The rate of hydrolysis of iodopentaaquochromium(III) ion has been measured as a function of pressure (0.1 to 250 MPa) and hydrogen ion concentration (0.1 to 1.0 mol kg−1) at 298.2 K and ionic strength 1.0 mol kg−1 (aqueous HClO4–LiClO4). The volumes of activation for the acid independent and inversely acid dependent hydrolysis pathways are −5.4 ± 0.5 and −1.6 ± 0.3 cm3 mol−1 respectively, and are not detectably pressure-dependent. Consideration of these values, together with the molar volume change of −3.3 ± 0.3 cm3 mol−1 determined dilatometrically for the completed hydrolysis reaction, indicates that the mechanisms of the two pathways are associative interchange (Ia) and dissociative conjugate base (Dcb) respectively.

A Raman Spectral Study of the Kinetics of Hydrolysis of Acetonitrile Catalyzed by Hg(II)

1975 ◽  
Vol 53 (3) ◽  
pp. 427-436 ◽  
Author(s):  
Yu-Keung Sze ◽  
Donald E. Irish
Keyword(s):  
Time Span ◽  
Water Molecules ◽  
Specific Rate ◽  
Ammine Complexes ◽  
Kinetics Of Hydrolysis ◽  
Specific Rate Constant ◽  
Rate Of Hydrolysis ◽  
Raman Spectral ◽  
Kinetics Of ◽  
Hydrolysis Of

Raman spectroscopy has been employed to follow the relatively slow rate of hydrolysis of acetonitrile, catalyzed by mercury(II). Raman lines at 2275 and 2305 cm−1 are characteristic of CH3CN bound to Hg2+, and are distinct from lines of bulk solvent. The intensities of these new lines decrease with time. From the intensities, concentrations of bound acetonitrile, [CH3CN]B were calculated for a time span of 400 min. The data fit a second order rate law: Rate = k[CH3CN]B[H2O]. The specific rate constant, k, obtained from four sets of data for the system Hg(ClO4)2–CH3CN–H2O equals 1.05 ± 0.06 × 10−4 mol−1 1 min−1 at 25 °C. The energy of activation is 18.9 kcal mol−1. In the proposed mechanism water molecules attack acetonitrile molecules which are bound to Hg2+ and form a mercury(II)–acetamide complex. Raman lines characteristic of this species are observed. This species slowly converts to mercury(II) ammine complexes and acetic acid. Anions which coordinate with Hg2+ more strongly than CH3CN, such as nitrate or acetate, slow or prevent the hydrolysis reaction.

scholarly journals Phenylcarbamic acid derivatives with integrated n-phenylpiperazine moiety in the structure – kinetics of alkaline hydrolysis study / Deriváty kyseliny fenylkarbámovej s integrovanou n-fenylpiperazínovou zložkou v štruktúre – štúdium kinetiky alkalickej hydrolýzy

2015 ◽  
Vol 62 (2) ◽  
pp. 38-42
Author(s):  
Stankovičová M. ◽  
Miháliková V. ◽  
Mezovský Ľ. ◽  
Lašáková A. ◽  
Medlenová V. ◽  
...  
Keyword(s):  
Alkaline Hydrolysis ◽  
Phenyl Ring ◽  
Arrhenius Equation ◽  
Sodium Hydroxide Solution ◽  
Antimycobacterial Activity ◽  
First Order ◽  
Rate Of Hydrolysis ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Hydrolysis Of

AbstractIn present work, we have studied kinetics of alkaline hydrolysis of 14 compounds, which are phenylcarbamic acid derivatives with integrated N-phenylpiperazine moiety in the structure. The compounds possessed moderate antiarrhythmic and antimycobacterial activity. Their hydrolysis was carried out in an aqueous medium ethanol sodium hydroxide solution. The course of the hydrolysis was observed spectrophotometrically in visible as well as in ultraviolet regions. The pseudo-first order rate constants were calculated at several temperatures. The values of the activation energy EAwere determined by the Arrhenius equation. The rate of hydrolysis of the compounds under the study increase with the increase in temperature and it has been differentiated according to the substitution of N-phenylpiperazine as well as to the alkoxy substitution on phenyl ring.

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