Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interaction of H+-ATPase complex F1 X F0 with the Trk system of K+ accumulation in E. coli grown quasi-anaerobically in pepton media with glucose (anaerobia) and aerobically in the salt medium with succinate (aerobia) treated with cyanide was studied. The ratio of H+ fluxes via F1 X F0 and K+ fluxes via the Trk system is stable and equals 2 in anaerobia and is changed from 0.5 to 5.0 in aerobia treated with cyanide in response to pH variation, K+ activity and temperature variations. Q10 is about 2.8 both for F1 X F0 and the Trk system in anaerobia, but 2.4 and 1.0 respectively in aerobia. K+ distribution in anaerobia reaches high values, K+ equilibrium potential is much higher than the measured membrane potential. K+ distribution in aerobia is smaller, which is in conformity with the measured membrane potential. Structural association of F1 X F0 and the Trk system with the formation of H+--K+-pump is assumed to take place in anaerobia, and separate operation of these systems occurs in aerobia, transfer of K+ via Trk system being energized by the electric field on the membrane.
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PMID:[Interaction of H+ and K+ transport systems in E. coli growing under anaerobic and aerobic conditions]. 287 28

H+-K+-exchange via the Trk-like system of K+ accumulation takes place in anaerobically grown S. typhimurium LT-2 with stable ratio of DCC-sensitive ionic fluxes, equal to 2H+ of a cell for one K+ of the medium. This exchange is now observed in the mutant S. typhimurium TH-31 with unfunctional H+-ATPase. H+-K+-exchange in aerobically grown S. typhimurium LT-2 has unstable ratio of ionic fluxes. The rate of K+ uptake in anaerobically grown bacteria is higher than that in the aerobically grown ones. Q10 is about 1.8 both for H+ transfer and K+ uptake in anaerobically grown bacteria, but it is 1.7 and 0.9 respectively in the aerobically grown ones. Delta psi is not changed by different temperatures both in anaerobically and aerobically grown bacteria. The distribution of K+ in anaerobically grown bacteria is higher than 10(3) and the potassium equilibrium potential is much higher than the measured delta psi. In aerobically grown bacteria the distribution of K+ is in good conformity with the measured delta psi. H+ and K+ transport in anaerobically grown cells is likely to proceed by the same mechanism, which includes H+-ATPase and the Trk-like system. In aerobically grown bacteria these transport systems work separately, and the Trk-like system as K+-ionophore serving for K+ uptake across the electrical field on the membrane.
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PMID:[The nature of H+-K+-exchange in anaerobically and aerobically grown S. typhimurium]. 288 75

The effect of a wide range of temperature on the development of twitch and tetanic tension was investigated in directly stimulated rat fast (EDL) and slow (SOL) twitch muscle preparations. When increasing the temperature from 6 to 30 degrees C the maximum tetanic tension rose steadily. The Q10 was 2.3 (EDL) and 2.7 (SOL) for temperatures between 12 and 22 degrees C. The twitch tension output of SOL muscle increased up to 36-38 degrees C, whereas the EDL muscle exhibited a distinct maximum at 22 degrees C followed by a 50% decrease at 34 degrees C. Post-tetanic potentiation was observed in EDL muscle at temperatures higher than 20 degrees C. In SOL muscle neither posttetanic potentiation nor cold potentiation could be observed. The twitch/tetanus ratio was 0.2-0.3 at 35 degrees C but 0.7-0.8 at 6 degrees C. In both muscle types the most characteristic effect of temperature was the prolongation of the time to peak and the relaxation time in parallel to cooling. The tension rise of fast twitch rat muscle during cooling from 35 degrees C downwards can be compared to the cold potentiation of frog sartorius muscle. It is suggested that the main effect of temperature on muscle function concerns the process of Ca2+ release and of Ca2+ uptake. The different response of SOL muscle may be related to the less developed sarcoplasmic reticulum and the lower Ca2+ ATPase activity.
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PMID:Contractile properties of fast and slow twitch muscles of the rat at temperatures between 6 and 42 degrees C. 344 7

A new DNA-dependent ATPase named ATPase IV has been purified to apparent homogeneity from Escherichia coli as a by-product of DNA polymerase III purification. The enzyme has a specific activity of 360 mumol of ATP hydrolyzed per min/mg of protein. The purified enzyme exists as monomer with a molecular weight of 81,000. It sediments in a glycerol gradient as a single species of 4.5 S. The enzyme has considerable activity at 0 degree C and has a Q10 of 3.8. In the presence of a DNA effector and magnesium ion, the enzyme will hydrolyze ATP, dATP, GTP, or dGTP to a nucleoside diphosphate plus orthophosphate with a Km of 0.20, 0.50, 0.60, and 1.30 mM, respectively. The guanine nucleotides, however, are only 25-35% as effective as substrates compared with the adenine nucleotides. ATPase IV shows strong substrate inhibition by ATP, but not dATP, above 0.2 mM. The polynucleotide effector requirement can be satisfied by either single-stranded or double-stranded DNA. The enzyme binds the effector very tightly with a Km of 3 X 10(-8) M (nucleotide) for G4 DNA. The enzyme is inhibited by E. coli single-stranded DNA-binding protein, a variety of ATP analogues and N-ethylmaleimide. The relationship of ATPase IV to DNA polymerase III holoenzyme is discussed.
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PMID:A new DNA-dependent ATPase from Escherichia coli. Purification and characterization of ATPase IV. 614 53

Isolated rat and mouse extensor digitorum longus (EDL) and soleus muscles were studied under isometric and isotonic conditions at temperatures from approximately 8 degrees -38 degrees C. The rate constant for the exponential rise of tension during an isometric tetanus had a Q10 of approximately 2.5 for all muscles (corresponding to an enthalpy of activation, delta H = 66 kJ/mol, if the rate was determined by a single chemical reaction). The half-contraction time, contraction time, and maximum rate of rise for tension in an isometric twitch and the maximum shortening velocity in an isotonic contraction all had a similar temperature dependence (i.e., delta H approximately 66 kJ/mol). The Mg++ ATPase rates of myofibrils prepared from rat EDL and soleus muscles had a steeper temperature dependence (delta H = 130 kJ/mol), but absolute rates at 20 degrees C were lower than the rate of rise of tension. This suggests that the Mg++ ATPase cycle rate is not limiting for force generation. A substantial fraction of cross-bridges may exist in a resting state that converts to the force-producing state at a rate faster than required to complete the cycle and repopulate the resting state. The temperature dependence for the rate constant of the exponential decay of tension during an isometric twitch or short tetanus (and the half-fall time of a twitch) had a break point at approximately 20 degrees C, with apparent enthalpy values of delta H = 117 kJ/mol below 20 degrees C and delta H = 70 kJ/mol above 20 degrees C. The break point and the values of delta H at high and low temperatures agree closely with published values for the delta H of the sarcoplasmic reticulum (SR) Ca++ ATPase. Thus, the temperature dependence for the relaxation rate of a twitch or a short tetanus is consistent with that for the reabsorption rate of Ca++ into the SR.
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PMID:Temperature dependence of mammalian muscle contractions and ATPase activities. 621 23

Single muscle fibres were isolated from the fast myotomal muscle of the teleost Myoxocephalus scorpius L. and chemically skinned with 1% Brij. Maximum Ca2+-activated force (P0) increased from 14.5 +/- 1.1 N cm-2 at 2 degrees C to 19.1 +/- 1.8 N cm-2 at 15 degrees C (mean +/- S.E.). Maximum contraction velocity was determined by Hill's slack-test method (V0) and by extrapolation from force-velocity (P-V) relationships (Vmax). There was a linear relation between log10 V0 and temperature below 15 degrees C (Q10 = 1.9, P less than 0.01). The force-velocity characteristics of the fibres were determined at 2 degrees C and 20 degrees C. Points below 0.6 P0 on the P-V curve could be fitted by a linear form of Hill's equation. Extrapolated Vmax values were 0.55 muscle lengths s-1 (L0 s-1) at 2 degrees C and 1.54 L0 s-1 at 20 degrees C. Curvature of the P-V relationship was independent of temperature. The Mg2+, Ca2+-ATPase activity of Triton-X 100 extracted myofibrils was determined under similar ionic conditions to those used in skinned fibre experiments. (Ionic strength 0.16 mmol l-1, pMgATP 2.5). A linear relationship between log10 ATPase and temperature was only obtained below 15 degrees C (P less than 0.001). Above 15 degrees C, the Q10 for ATPase decreased significantly. The Q10(0-15 degrees C) for ATPase activity (3.9) was significantly higher than for unloaded contraction velocity. Supercontraction of isolated myofibrils to very short sarcomere lengths and differences in the mechanical constraints for crossbridge cycling between the preparations probably account for the lack of proportionality between these two parameters.
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PMID:Differences in temperature dependence of muscle contractile properties and myofibrillar ATPase activity in a cold-temperature fish. 623 19

Ca2+-dependent ATPase (Ca2+-dependent ATP phosphohydrolase, EC 3.6.1.3) present in a subcellular fraction derived from rat pancreatic islet homogenates was examined to determine kinetic parameters and responses to various substances with known effects upon insulin secretion. Experiments demonstrated the presence of a Ca2+-ATPase with a Km ATP of 7 . 10(-5) M and two Km Ca of 1.3 . 10(-7) M and 5.7 . 10(-6) M. The enzyme had little activity in acidic media while retaining considerable activity in basic media. Optimal activity was obtained at pH 7.5. The enzyme was relatively temperature insensitive (Q10 = 1.49), since activity decreased less than 50% with a 15 degrees C decrease in temperature. Studies on the stability of enzyme activity upon storage at -20 degrees C indicated that for intact islets activity was stable for 3 weeks, while in homogenates activity was stable for only 1 week, after which activity rapidly declined in both cases. Certain substances known to either stimulate or inhibit insulin secretion were tested for their ability to alter enzyme activity. Potassium, glibenclamide and cyclic AMP had no effects upon activity. These observations are consistent with the hypothesis that a Ca2+-ATPase present in pancreatic islets may act as a modulator of pancreatic islet beta cell activity.
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PMID:Characterization of pancreatic islet Ca2+-ATPase. 627 67

Tension P0 and ATPase activity J0 of glycerinated single muscle fibers under isometric concentration as well as the velocity V0 of unloaded shortening were measured as a function of substrate concentration [S]. The stiffness of fibers with sinusoidal length changes at 1 kHz was used as a qualitative measure of the amount of rigor complex. P0 is an increasing function of [S] at low substrate concentrations and has a broad maximum at about 10-40 micrometers MgATP. In this concentration range, 10-40 micrometers, V0 still has a very small value. Then it increases and finally reaches at a plateau at about 1 mM MgATP. J0 increases as P0 does. However, it reaches at a saturated level at about the same concentration as V0. Either 0.5 mM 8-BrATP or 1 mM PPi was added to the substrate solutions to reduce the amount of rigor complex at low substrate concentrations. The addition of PPi of 8-BrATP decreases P0 dominantly at low concentrations of substrate and shifts the maximum to about 100 micrometers MgATP. 8-BrATP considerably increases V0 at low substrate concentrations while V0 is decreased by added PPi. The temperature coefficients, Q10 values were obtained for P0, J0, and V0. The values are essentially constant, 2.1-2.4, in the cases of P0 and J0, and about the same values were found for V0 at very low substrate concentrations. However, they become about 3.3 in the concentration range from 34 micrometers and 2.3 mM. The P-V relation was obtained at 11 micrometers and 2.3 micrometers MgATP. The normalized P-V relation at 11 micrometers was unchanged when 8-BrATP was added. The results are discussed in connection with the mechanism of actomyosin-ATPase activity as well as that of the elementary cycle of the motive force generation.
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PMID:Substrate-concentration of dependences of tension, shortening velocity and ATPase activity of glycerinated single muscle fibers. 627 76

1. A method has been developed to discriminate between the rate of ATP hydrolysis associated with calcium uptake into the sarcoplasmic reticulum (SR) and force development of the contractile apparatus in mechanically or saponin-skinned skeletal muscle fibres. The rate of ATP hydrolysis was determined in fibres of different types from the iliofibularis muscle of Xenopus laevis by enzymatic coupling of ATP re-synthesis to the oxidation of NADH. 2. The ATPase activity was determined before and after exposure of the preparations for 30 min to a solution containing 0.5% Triton X-100, which effectively abolishes the SR ATPase activity. The fibres were activated in a solution containing 5 mM caffeine to ensure that calcium uptake into the SR was maximal. 3. At saturating Ca2+ concentrations the actomyosin (AM) and SR ATPase activities in fast-twitch fibres, at 4.3 degrees C, amounted to 1.52 +/- 0.07 and 0.58 +/- 0.10 mumol s-1 (g dry wt)-1, respectively (means +/- S.E.M.; n = 25). The SR ATPase activity was 25% of the total ATPase activity. At submaximal calcium concentrations the AM ATPase activity varied in proportion to the isometric force. 4. The calcium sensitivity of the SR ATPase was larger than that of the AM ATPase and its dependence on [Ca2+] was less steep. The AM ATPase activity was half-maximal at a pCa of 6.11 (pCa = -log [Ca2+]) whereas the SR ATPase activity was half-maximal at a pCa of 6.62. 5. In Triton X-100-treated fibres, at different 2,3-butanedione monoxime (BDM) concentrations, the AM ATPase activity and isometric force varied proportionally. The SR ATPase activity determined by extrapolation of the total ATPase activity in mechanically skinned or saponin-treated fibres to zero force, was independent of the BDM concentration in the range studied (0-20 mM). The values obtained for the SR ATPase activity in this way were similar to those obtained with Triton X-100 treatment. 6. The AM ATPase activity in slow-twitch fibres amounted to 0.74 +/- 0.13 mumol s-1 (g dry wt)-1, i.e. about a factor of two smaller than in fast-twitch fibres. The SR ATPase activity amounted to 0.47 +/- 0.07 mumol s-1 (g dry wt)-1, i.e. rather similar to the value in fast-twitch fibres. The proportion of the total ATPase activity that was due to SR ATPase (40%) was larger than in fast-twitch fibres. 7. The temperature dependence of the AM and SR ATPase activities in fast-twitch fibres differed. In the temperature range 5-10 degrees C, the relative changes in AM and SR ATPase activities for a 10 degrees C temperature change (Q10) were 3.9 +/- 0.3 and 7.2 +/- 1.5, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:ATP utilization for calcium uptake and force production in skinned muscle fibres of Xenopus laevis. 773 Sep 76

1. In order to investigate mechanisms of Na+ transfer, the unidirectional maternal-fetal clearance (Kmf) of 22Na+ and of 51Cr-EDTA (a marker of paracellular diffusion) was measured across the intact or umbilically or dually perfused placenta of the anaesthetized rat. 2. The Kmf of 22Na+ in the intact preparation (18.5 +/- 2.7 microliters min-1, mean +/- S.D., n = 105 placentas) exceeded that of 51Cr-EDTA in the same experiments (1.4 +/- 0.3 microliters min-1) by more than ten times, whereas the difference in their diffusion coefficients in water was only 2-fold. In the perfused preparations the difference in the Kmf values was 6-fold. 3. Assuming that a simple model of paracellular diffusion through wide pores was one component of transfer, the Kmf of 51Cr-EDTA and the diffusion coefficients were used to calculate a component of 22Na+ clearance (Kmf,residual) and of Na+ flux (Jmf,residual) across the perfused placentas which could not be accounted for by transfer through the paracellular route. 4. Kmf,residual of 22Na+ across the dually perfused placenta was significantly lower when temperature was reduced, the temperature quotient (Q10) of the transfer being about 2. Kmf,residual was also significantly lower when 0.1 mM ouabain was perfused on the fetal side. Jmf,residual exhibited saturation kinetics characterized by an apparent Michaelis constant (Km) of 90 mM. Kmf,residual was not influenced by 0.5 mM frusemide, 0.5 mM amiloride or by 0.5 mM hydrochlorothiazide administered to the maternal side. It was significantly increased by 1 mM alanine on the maternal side suggesting that the coupled transfer of Na+ and amino acids may contribute significantly to the maternal-fetal flux of Na+. 5. These observations suggest that most (80%) of the maternal-fetal flux of Na+ across the rat placenta is effected by active transcellular transport. This transport involves passive entry of Na+ into the trophoblast from the maternal side by a largely unknown saturable mechanism and active extrusion of Na+ from trophoblast to the fetal side by Na(+)-K(+)-ATPase.
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PMID:Evidence for active maternal-fetal transport of Na+ across the placenta of the anaesthetized rat. 830 47


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