Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myosin was extracted from frozen squid brain and purified by a modification of the procedure of Pollard et al. (Pollard, T.D., Thomas, S.M., and Niederman, R. (1974) Anal. Biochem. 60, 258-266). Myosin was eluted from Bio-Gel A-15m column as a single peak of (K+-EDTA)-activated ATPase ((K+-EDTA)-ATPase) activity with an average partition coefficient (Kav) of 0.22. In sodium dodecyl sulfate-acrylamide gel electrophoresis, the purified myosin showed a predominant band with similar electrophoretic mobility as the heavy chain of rabbit skeletal muscle myosin, and two less intense bands near the bottom of the gel. No actin band was seen. The properties of the (K+-EDTA)-ATPase activity were: (a) the time course of the reaction was biphasic at 25 degrees but linear at 32 degrees; (b) the optimum rate of reaction was obtained between 0.3 and 0.8 M KCl; (c) the pH optimum was between 8.0 and 9.0; (d) the reaction was specific for ATP with an apparent Km of 0.19 mM. ATPase activity in 0.06 M KCl and 5 mM MgCl2 was increased about 1.5 times by a 10-fold excess of rabbit skeletal muscle F-actin and about 5 times by a 40-fold excess. The actin activation was inhibited slightly by the addition of 0.2 mM CaCl2 and completely by the addition of 10 mM CaCl2. Myosin formed arrowhead patterns with rabbit skeletal muscle F-actin as observed by electron microscopy of negatively stained samples. It also aggregated in bipolar filaments which attached to decorated actin filaments at different angles, as well as formed cross-connections and ladder-like patterns between actin filaments. These two forms of interactions between myosin and actin were abolished by treatment with MgATP.
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PMID:Purification and characterization of squid brain myosin. 13 40

A partially purified soluble ATPase (ATP phosphohydrolase, EC 3.6.1.3) from pea cotyledon mitochondria was characterized. Inhibition patterns with azide, NaF, and cold, and a stimulation by 2,4-dinitrophenol were typical of F1-ATPases from mammalian mitochondria. The enzyme hydrolysed GTP, ITP, and ATP, but not CTP, UTP, ADP, or IDP. ATPase and ITPase activities were strongly inhibited by ADP and to a lesser extent by IDP. Distinctive properties of the pea mitochondrial enzyme were activation by high concentrations of CaCl2 and stimulation by NaCl.
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PMID:Partial characterization of a soluble ATPase from pea cotyledon mitochondria. 14 76

The characteristics of the anion-sensitive Mg2+-ATPase activity of the rabbit erythrocyte have been studied in a lyophilized ghost preparation. The enzyme appears to be different from the anion-sensitive Mg2+-ATPase activity of other tissues in many parameters, such as optimal pH, effects of various anions, oligomycin sensitivity and effects of Triton X-100. The enzyme is insensitive towards inhibition by irreversibly bound 4,4'-diisothiocyano-dihydrostilbene-2,2'-disulfonic acid (H2DIDS). This excludes a relationship between the enzyme and the "band 3" protein, which is thought to be involved in the anion exchange over the erythrocyte membrane. From the effects of ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA), CaCl2, chlorpromazine and ruthenium red it is concluded that the enzyme activity does not represent a separate entity but is part of the (Ca2+ + Mg2+)-ATPase system of the erythrocyte membrane. A reported stimulatory effect of carbonic anhydrase is attributed to a contamination of the carbonic anhydrase preparation by calcium and/or (Ca2+ + Mg2+)-ATPase activator protein.
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PMID:Is there a plasma membrane-located anion-sensitive ATPase? III. Identity of the erythrocyte enzyme with (Ca2+ + Mg2+)-ATPase. 14 18

The soluble ATPase (adenosine triphosphatase) from Micrococcus lysodeikticus underwent a major unfolding transition when solutions of the enzyme at pH 7.5 were heated. The midpoint occurred at 46 degrees C when monitored by changes in enzymic activity and intrinsic fluorescence, and at 49 degrees C when monitored by circular dichroism. The products of thermal denaturation retained much secondary structure, and no evidence of subunit dissociation was detected after cooling at 20 degrees C. The thermal transition was irreversible, and thiol groups were not involved in the irreversibility. The presence of ATP, adenylyl imidodiphosphate, CaCl2 or higher concentrations of ATPase conferred stability against thermal denaturation, but did not prevent the irreversibility one denaturation had taken place. In the presence of guanidinium chloride, thermal denaturation occurred at lower temperatures. The midpoints of the transition were 45 degrees C in 0.25 M-, 38 degrees C in 0.5 M-and 30 degrees C in 0.75 M-denaturant. In the highest concentration of guanidinium chloride a similar unfolding transition induced by cooling was observed. Its midpoint was 9 degrees C, and the temperature of maximum stability of the protein was 20 degrees C. The discontinuities occurring the the Arrhenius plots of the activity of this enzyme had no counterpart in variations in the far-u.v. circular dichroism or intrinsic fluorescence of the protein at the same temperature.
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PMID:Thermal denaturation of Micrococcus lysodeikticus adenosine triphosphatase. Influence of temperature on the circular dichroism, fluroescence and enzymic activity of the protein. 14 80

The steady state kinetics of ATP hydrolysis by partially purified adenosine triphosphatase preparations of sarcoplasmic reticulum was investigated at 0 degrees C and pH 7.0 in 2.0 mM MgCl2, 20 microM [gamma-32P]ATP, 20 microM CaCl2, and various concentrations of KCl in the presence and absence of 12% dimethyl sulfoxide. The steady state phosphoenzyme formed under these conditions could be resolved kinetically into ADP-sensitive and ADP-insensitive forms. These steady state kinetic data were analyzed according to a scheme in which the ADP-sensitive and ADP-insensitive phosphoenzymes occur sequentially, and Pi is derived from the latter. The KCl-dependent turnover rate of the ADP-insensitive phosphoenzyme that was estimated according to this scheme was in good agreement with the directly measured hydrolysis rate constant of the ADP-insensitive phosphoenzyme. In addition, the time course of the decomposition of the total amount of phosphoenzyme, measured after a steady state level was reached in 20 mM KCl and further phosphorylation was prevented by addition of excess ethylene glycol bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid, was also in agreement with that calculated according to this scheme using values of the rate constants estimated from the amounts of the ADP-sensitive and ADP-insensitive phosphoenzymes and the rate of ATP hydrolysis. These results, together with our previous findings, support the view that this scheme describes the mechanism of ATP hydrolysis in the presence of KCl.
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PMID:On the mechanism of Ca2+-dependent adenosine triphosphatase of sarcoplasmic reticulum. Occurrence of two types of phosphoenzyme intermediates in the presence of KCl. 15 97

Fluorescent cyanine (diS-C3-(5), diS-C2-(5), diO-C3-(5)) and oxonol (diBA-C4-(5)) potential-dependent dyes appeared to be extremely effective in detecting and studying the potential formed on the fragmented sarcoplasmic reticulum membrane under Ca2+ transport When [Ca2+] less than 5 X 10(-7) M ATP hydrolysis leads to formation of transmembrane potential (positive inside vesicules) caused by the Ca-independent ATPase activity. The potential is formed by a monovalent ion, presumably by H+, and possibly by Mg2+ ions. Ca-dependent ATPase activation by Ca2+ makes the potential to drop sharply and successive Ca2+ transport proceeds at low potential value. When Ca2+ has been accumulated by vesicules the Ca-independent ATPase restores positive potential. The potentials generated by both Ca-independent (10--30 mv) and Ca-dependent (-20 divided by -40 mv) ATPases have been estimated on the basis of the Nernst's equation with the help of positive and negative diffusion potentials formed by MgCl2 and CaCl2 gradients. The Ca2+ transport is shown not to be due to transmembrane electrophoresis but Ca-dependent ATPase action. The results suggest quite clearly that Ca-dependent ATPase operates as electrogenic Ca2+/H+, Mg2+-exchanger. The functional role of Ca-independent ATPase is, possibly, in compensation of charge effects when Ca2+ ions are passing through the membranes. The model illustrating the electrogenicity of Ca-independent and Ca-dependent ATPases action during Ca2+ transport in SR membranes has been proposed.
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PMID:[Transmembrane potential formation upon ATP hydrolysis in sarcoplasmic reticulum]. 15 68

1. Subcellular fractions obtained from epimastigotes of Trypanosoma cruzi, disrupted by three different procedures, contained in addition to the already known Mg2+-activated adenosine triphosphatase (ATPase; E.C.3.6.1.4), a Ca2+-ATPase activity. 2. The Ca2+-ATPase (a) was activated by low concentrations of CaCl2 (apparent Ka, 80 microM); (b) had a Km for ATP of 0.6 mM (at 1 mM CaCl2, pH 8.0); (c) presented a broad pH curve (optimum 7.1-8.6); and (d) was insensitive to oligomycin concentrations which inhibited the Mg2+-ATPase present in the same preparations. 3. All attempts to find a (Na+-K+)-activated, ouabain-inhibited, ATPase have been unsuccessful, in spite of the fact that living epimastigoes of T. cruzi are able to concentrate K+ and exclude Na+ from the medium.
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PMID:Adenosine triphosphatase activities in Trypanosoma cruzi. 16 83

1. Grinding of epimastigotes of Trypanosoma cruzi with glass powder in a mortar yielded a Mg2+-activated adenosine triphosphatase (ATPase) preparation which was highly sensitive to oligomycin. 2. Chloroform treatment of the particles resulted in the solubilization of an ATPase which was (a) activated by MgCl2; (b) slightly inhibited by CaCl2; (c) activated by sulphite and bisulphite; (d) had an optimum pH of 7.6; and (e) had a Km for ATP of 2.1 mM (in the presence of 4 mM MgCl2). 3. The solubilized enzyme was insensitive to oligomycin and leucinostatin, which inhibited the membrane-bound ATPase, though inhibited by efrapeptin and quercetin. 4. The results indicate that the chloroform-extracted enzyme is a soluble F1-ATPase similar to those isolated from mammalian mitochondria.
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PMID:Solubilization and some properties of the Mg2+-activated adenosine triphosphatase from Trypanosoma cruzi. 16 84

The nucleoside triphosphatase [EC 3.6.1.15] activity of actomysin and that of myosin are measured by varying the concentration of nucleoside triphosphate and that of CaCl2 or MgGl2. The results thus obtained are examined by asking a question of which is responsbile for the activity, the true substrate and the active enzyme in terms of the reaction scheme shown in p. 719. The answers found for the above question are summarized in Table I (see p. 720). It is emphasized that the summmary (Table I) corresponds very well to the fact that myosin alone does not superprecipitate in the presence of either calcium or magnesium ions, whereas actomyosin does superprecipitate in the presence of magnesium ions and not in the presence of calcium ions. Obviously, the true substrate type of reaction scheme represents a kinetic property characteristic of the superprecipitation-coupled nucleoside-triphosphatase. It is also noted of the summary (Table I) that actin is capable of not only activating Mg-nucleoside-triphosphatase but also switiching the reaction scheme from the active enzyme type to the true substrate type. It is known that trinitrophenylation of myosin results in activation of the Mg-ATPase activity of myosin. However, it is now found that trinitrophenylation is not capable of switiching the reaction scheme, that is to say that the Mg-ATPase reaction of trinitrophenyl-myosin stays with the active enzyme type of reaction scheme and that of acto-trinitrophenyl-myosin with the true substrate type of reaction scheme. Effect of actin on the function of myosin seems, therefore, very unique.
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PMID:A new kinetic property characteristic of the actomyosin-nucleoside-triphosphatase. 17 88

In order to investigate the roles of the physical states of phospholipid and protein in the enzymatic behavior of the Ca2+ -ATPase from sarcoplasmic reticulum, we have modified the lipid phase of the enzyme, observed the effects on the enzymatic activity at low temperatures, and correlated these effects with spectroscopic measurements of the rotational motions of both the lipid and protein components. Replacement of the native lipids with dipalmitoyl phosphatidylcholine inhibits ATPase activity and decreases both lipid fluidity, as monitored by EPR spectroscopy on a stearic acid spin label, and protein rotational mobility, as monitored by saturation transfer EPR spectroscopy on the covalently spin-labeled enzyme. Solubilization of the lipid-replaced enzyme with Triton X-100 reverses all three of these effects. Ten millimolar CaCl2 added either to the enzyme associated with the endogenous lipids or to the Triton X-100 soulbilized enzyme inhibits both ATPase activity and protein rotational mobility but has no detectable effect on the lipid mobility. These results are consistent with the proposal that both lipid fluidity and protein rotational mobility are essential for enzymatic activity.
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PMID:Effect of the lipid environment on protein motion and enzymatic activity of sarcoplasmic reticulum calcium ATPase. 21 Nov 34


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