Interaction of Actomyosin and Adenosinetriphosphate as Studied With Glycerol-Extracted Cardiac Muscle Bundles

1958 ◽  
Vol 194 (3) ◽  
pp. 564-572 ◽  
Author(s):  
Ellis S. Benson ◽  
Ben E. Hallaway
Keyword(s):  
Ionic Strength ◽  
Atp Hydrolysis ◽  
Divalent Cations ◽  
Isometric Tension ◽  
Tension Development ◽  
Sodium Magnesium ◽  
Rate Of Hydrolysis ◽  
Effects Of Temperature ◽  
The Right ◽  
Hydrolysis Of

Glycerol-extracted muscle bundles were obtained from the right and left ventricles of dogs. Isometric tension developed on addition of adenosinetriphosphate (ATP) and resistance to stretch of the extracted bundles and the rate of ATP hydrolysis of the myofibrillar components of the bundle were studied. Effects of temperature, ionic strength, pH and concentrations of ATP, sodium, magnesium and calcium were evaluated. The results indicated that the contractile phenomenon producing tension is a complex of at least two underlying reactions one of which promotes contraction ( R1) and the other ( R2) relaxation. Which of these reactions limits tension development is determined by the concentration of ATP. The concentration at which the transition takes place between R1 as the limiting reaction to R2 is a function of temperature, ionic strength, pH and the concentration of calcium ions. R1 appears to be associated with the hydrolysis of ATP and this may be the energy-supplying reaction. Certain findings in regard to the effect of concentration of divalent cations on the contractile response and the rate of hydrolysis are difficult to reconcile, however, with the contention that R1 is a reaction in which ATP is hydrolyzed. At very low concentration of Mg and Ca, hydrolysis is strikingly inhibited though contraction takes place. Furthermore, concentrations of Mg of the order of 2 x 10–2 m inhibit enzymatic hydrolysis and promote contraction. Concentrations of Ca of 10–2 m inhibit contraction but accelerate ATP hydrolysis.

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.

ÉTUDE DES EFFETS ÉLECTROSTATIQUES SUR LE MÉCANISME D'ACTION CATALYTIQUE DE LA PHOSPHATASE ALCALINE INTESTINALE DE VEAU

1965 ◽  
Vol 43 (8) ◽  
pp. 2222-2235 ◽  
Author(s):  
Michel Lazdunski ◽  
Jacques Brouillard ◽  
Ludovic Ouellet
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Maximum Activity ◽  
Enzyme Molecule ◽  
High Substrate Concentration ◽  
Nitrophenyl Phosphate ◽  
Phosphatase Alcaline ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Activated Complex

The influence of dioxane and ethanol on the rate of hydrolysis of p-nitrophenyl phosphate in the presence of an intestinal alcaline phosphatase can be interpreted as a dielectric constant effect, at high substrate concentration. The dielectric constant effect is a function of the pH of the medium and is maximum around pH 9.4 at 25 °C and pH 9.0 at 15 °C. An interpretation suggesting that the change in diameter of the enzyme molecule becoming an activated complex is minimum at a pH of maximum activity is proposed. The same model can take into account the influence of the ionic strength on the same reaction.

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.

Effects of active shortening on tension development of rabbit papillary muscle

1980 ◽  
Vol 238 (1) ◽  
pp. H8-H13 ◽  
Author(s):  
J. K. Leach ◽  
A. J. Brady ◽  
B. J. Skipper ◽  
D. L. Millis
Keyword(s):  
Isometric Tension ◽  
Isometric Contractions ◽  
Tension Development ◽  
Velocity Of Shortening ◽  
Tension Time ◽  
Shortening Deactivation ◽  
Force Velocity ◽  
Stimulus Length ◽  
The Right ◽  
The Hill

Duration and intensity of force development have been shown to be less during active muscle shortening than during isometric contraction. The purpose of this study was to compare force developed during controlled shortening with that predicted by the Frank-Starling relation. Paillary muscles from the right ventricles of rabbits were arranged for isometric tension recording, and isometric contractions were recorded at several lengths. The muscles were then permitted to shorten at velocities of 0.2--6 mm/s, shortening beginning 150--200 ms after the stimulus. Length-tension-time curves constructed from the isometric contractions were used to determine predicted shortening tension (Pp), which was compared with actual tension during shortening (Ps) at corresponding times and lengths. Ps was significantly less than Pp and the ratio Ps/Pp decreased with increasing velocity of shortening. The decrease in Ps/Pp was directly related to the duration of shortening (P less than 0.001), suggesting that the fall of shortening tension reflected both the Hill force-velocity relation and shortening deactivation.

An ATP-inhibited soluble 5'-nucleotidase of rat kidney

1988 ◽  
Vol 254 (2) ◽  
pp. F191-F195
Author(s):  
M. Le Hir ◽  
U. C. Dubach
Keyword(s):  
High Speed ◽  
Catalytic Properties ◽  
Divalent Cations ◽  
Rat Kidney ◽  
Maximal Activity ◽  
Rate Of Hydrolysis ◽  
Membrane Bound ◽  
Ph Range ◽  
Hydrolysis Of

Hydrolysis of 5'-AMP by 5'-nucleotidase is a possible source of adenosine in the kidney. A renal membrane-bound ecto-5'-nucleotidase has been previously described. The present study deals with the catalytic properties of a 5'-AMP phosphohydrolase partially purified from high-speed supernatants of rat kidney homogenates. It exhibits phosphatase activity toward 5'-AMP, 5'-IMP, and 5'-GMP, but not toward 2'- and 3'-AMP and corresponds therefore to a 5'-nucleotidase. The hydrolysis of 5'-AMP by the soluble 5'-nucleotidase requires divalent cations. Maximal activity is reached with 10 microM of either Mn2+ or Co2+, whereas half-maximal activity is obtained with approximately 400 microM Mg2+. The soluble 5'-nucleotidase exhibits Michaelis-Menten kinetics with a Km of 9.5 microM for 5'-AMP. In the presence of 1 mM of free Mg2+, physiological concentrations of ATP provoke an increase of the Km for 5'-AMP and a decrease of Vmax. An increase of the pH of 0.4 units in the pH range 6.4-7.4 roughly doubles the rate of hydrolysis of 5'-AMP. The effects of ATP and of the pH are compatible with a role of the renal soluble 5'-nucleotidase in the hydrolysis of 5'-AMP and in the production of adenosine during hypoxia.

scholarly journals Properties of methyl acetimidate and its use as a protein-modifying reagent

1981 ◽  
Vol 193 (1) ◽  
pp. 245-249 ◽  
Author(s):  
A J Makoff ◽  
A D B Malcolm
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Reaction Mechanisms ◽  
Effect Of Ph ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The rate of hydrolysis of the imido ester methyl acetimidate and its rate of amidination of denatured aldolase were investigated under different conditions of temperature, pH and ionic strength. Both rate constants increase greatly with temperature, whereas ionic strength has no effect on either. The effect of pH is more complex. Between pH 6.8 and 8.8 the rate of hydrolysis decreases and the rate of amidination increases. These results are discussed in terms of the reaction mechanisms involved.

Measurement of activation energy and oxidative phosphorylation onset kinetics in isolated muscle fibers in the absence of cross-bridge cycling

2006 ◽  
Vol 290 (6) ◽  
pp. R1707-R1713 ◽  
Author(s):  
B. Walsh ◽  
R. A. Howlett ◽  
C. M. Stary ◽  
C. A. Kindig ◽  
M. C. Hogan
Keyword(s):  
Activation Energy ◽  
Atp Hydrolysis ◽  
Muscle Fibers ◽  
Metabolic Cost ◽  
Oxygen Uptake Kinetics ◽  
Isometric Tension ◽  
Isometric Contractions ◽  
Fiber Types ◽  
Tension Development ◽  
Cross Bridge

This study utilized N-benzyl- p-toluene sulfonamide (BTS), a potent inhibitor of cross-bridge cycling, to measure 1) the relative metabolic costs of cross-bridge cycling and activation energy during contraction, and 2) oxygen uptake kinetics in the presence and absence of myosin ATPase activity, in isolated Xenopus laevis muscle fibers. Isometric tension development and either cytosolic Ca2+ concentration ([Ca2+]c) or intracellular Po2 (P[Formula: see text]) were measured during contractions at 20°C in control conditions (Con) and after exposure to 12.5 μM BTS. BTS attenuated tension development to 5 ± 0.4% of Con but did not affect either resting or peak [Ca2+]c during repeated isometric contractions. To determine the relative metabolic cost of cross-bridge cycling, we measured the fall in P[Formula: see text] (ΔP[Formula: see text]; a proxy for V̇o2) during contractions in Con and BTS groups. BTS attenuated ΔP[Formula: see text] by 55 ± 6%, reflecting the relative ATP cost of cross-bridge cycling. Thus, extrapolating ΔP[Formula: see text] to a value that would occur at 0% tension suggests that actomyosin ATP requirement is ∼58% of overall ATP consumption during isometric contractions in mixed fiber types. BTS also slowed the fall in P[Formula: see text] (time to 63% of overall ΔP[Formula: see text]) from 75 ± 9 s (Con) to 101 ± 9 s (BTS) ( P < 0.05), suggesting an important role of the products of ATP hydrolysis in determining the V̇o2 onset kinetics. These results demonstrate in isolated skeletal muscle fibers that 1) activation energy accounts for a substantial proportion (∼42%) of total ATP cost during isometric contractions, and 2) despite unchanged [Ca2+]c transients, a reduced rate of ATP consumption results in slower V̇o2 onset kinetics.

scholarly journals Structural evidence for the roles of divalent cations in actin polymerization and activation of ATP hydrolysis

2018 ◽  
Vol 115 (41) ◽  
pp. 10345-10350 ◽  
Author(s):  
Clement P. M. Scipion ◽  
Umesh Ghoshdastider ◽  
Fernando J. Ferrer ◽  
Tsz-Ying Yuen ◽  
Jantana Wongsantichon ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Actin Polymerization ◽  
Atp Hydrolysis ◽  
Divalent Cations ◽  
Md Simulations ◽  
Cumulative Probability ◽  
X Ray ◽  
Rate Of Hydrolysis ◽  
Protein Components ◽  
Cation Sites

The structure of the actin filament is known at a resolution that has allowed the architecture of protein components to be unambiguously assigned. However, fully understanding the chemistry of the system requires higher resolution to identify the ions and water molecules involved in polymerization and ATP hydrolysis. Here, we find experimental evidence for the association of cations with the surfaces of G-actin in a 2.0-Å resolution X-ray structure of actin bound to a Cordon-Bleu WH2 motif and in previously determined high-resolution X-ray structures. Three of four reoccurring divalent cation sites were stable during molecular dynamics (MD) simulations of the filament, suggesting that these sites may play a functional role in stabilizing the filament. We modeled the water coordination at the ATP-bound Mg2+, which also proved to be stable during the MD simulations. Using this model of the filament with a hydrated ATP-bound Mg2+, we compared the cumulative probability of an activated hydrolytic water molecule approaching the γ-phosphorous of ATP, in comparison with G-actin, in the MD simulations. The cumulative probability increased in F-actin in line with the activation of actin’s ATPase activity on polymerization. However, inclusion of the cations in the filament lowered cumulative probability, suggesting the rate of hydrolysis may be linked to filament flexibility. Together, these data extend the possible roles of Mg2+ in polymerization and the mechanism of polymerization-induced activation of actin’s ATPase activity.

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

1977 ◽  
Vol 57 (3) ◽  
pp. 271-278 ◽  
Author(s):  
C. CHANG ◽  
G. J. RACZ
Keyword(s):  
Incubation Temperature ◽  
Sodium Tripolyphosphate ◽  
Phosphate Concentration ◽  
Water Soluble ◽  
Sodium Pyrophosphate ◽  
Hydrolysis Rate ◽  
Rate Of Hydrolysis ◽  
Effects Of Temperature ◽  
Hydrolysis Of ◽  
Pyrophosphate Hydrolysis

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.

The action of rennets on the caseins: I. Rennin action on β-casein-B in solution

1971 ◽  
Vol 38 (3) ◽  
pp. 269-280 ◽  
Author(s):  
L. K. Creamer ◽  
O. E. Mills ◽  
E. L. Richards
Keyword(s):  
Ionic Strength ◽  
Conformational Changes ◽  
Calcium Ion ◽  
Ion Concentration ◽  
Disk Electrophoresis ◽  
C Terminus ◽  
Rate Of Hydrolysis ◽  
Calcium Ion Concentration ◽  
Hydrolysis Of ◽  
Electrophoresis Technique

SummaryA study of the hydrolysis of β-casein-B by crystalline rennin or rennet extract at pH 6·5, using a disk electrophoresis technique, showed that 3 bonds in β-casein are appreciably more sensitive than the others to rennin proteolysis, and that these bonds are probably located near the C-terminus of the protein. The most susceptible bond is hydrolysed, at 10°C, about 200 times faster than any other bond, whilst at 37°C it is hydrolysed 60 times faster. A study of the hydrolysis of this bond showed that its rate of hydrolysis at 37°C and pH 6·5 is decreased by either increased ionic strength or increased calcium ion concentration at constant ionic strength. Conformational changes in the substrate are probably responsible for these effects.

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