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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Frozen sections of equine musculus semitendinosus were examined for myosin adenosine triphosphatase (ATPase) and reduced nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR), using standard histochemical procedures, and the proportions of the various fiber types and average fiber sectional size were determined. With ATPase staining, approximately 70% of the fibers were classified as alpha fibers (ATPase positive), and 30%, as beta fibers (ATPase negative). In addition, 2 populations of alpha fibers could be readily distinguished on the basis of the intensity of the ATPase reaction, and these were designated alpha positive and alpha intermediate. The relationship of this difference in ATPase reaction to contraction speed of the fibers is not known. With NADH-TR staining, fibers were classified as either red fibers (positive) having aerobic metabolism or white fibers (negative) having primarily anaerobic metabolism. All beta fibers were red by NADH-TR; thus, they conformed to the criteria for beta R fibers. All alpha positive fibers were white by NADH-TR, as were most of the alpha intermediate fibers, and would be classified alpha W. Some of the alpha intermediate fibers gave an intermediate reaction with NADH-TR and could be classified as alpha R fibers which have not transformed to alpha W fibers. The alpha positive fibers were 7 to 10 mum larger in diameter than either beta or alpha intermediate fibers.
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PMID:Fiber types and size in equine skeletal muscle. 13 Aug 14

A protein fraction from the cellular slime mold Dictyostelium discoideum confers Ca2+-sensitivity on the activation of purified myosin adenosinetriphosphatase (ATP phosphohydrolase, EC 3.6.1.3) from Dictyostelium by purified Dictyostelium actin. That is, the fraction inhibits the actomyosin adenosine triphosphatase activity in the absence of Ca+ but not in the presence of Ca2+. This Ca2+-sensitizing factor affects only the actin-activated myosin adenosine triphosphatase and not the enzyme activity of myosin alone. The Ca2+-sensitivity is conserved when muscle actin replaces Dictyostelium actin, but is lost when muscle myosin replaces Dictyostelium myosin. The factor appears to be a protein since it is nondialyzable, is heat labile, and can be precipitated with ammonium sulfate. The factor can be purified 70-fold on an actin-affinity column.
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PMID:Calcium control of actin-activated myosin adenosine triphosphatase from Dictyostelium discoideum. 13 52

Actin can be cleaved by trypsin or chymotrypsin into a large, autonomous fragment with approximately 80% of the mass of the undegraded polypeptide. The protease-resistant cores obtained with either enzyme are very similar. Although the fragment does not bind calcium ions and fails to polymerize to the filamentous form of actin or to stimulate myosin adenosine triphosphatase (ATP phosphohydrolase, EC 3.6.1.3) activity, it retains the full capacity to bind ATP. This observation suggests that it represents an independent functional unit. Cleavage of globular actin with either trypsin or chymotrypsin occurs with half-times of 3 min, while that of filamentous actin proceeds with reaction half-times of 20 min for trypsin and nearly 2 hr for chymotrypsin. Denaturation and renaturation of the trypsin-resistant core shows that approximately 20% of the molecules refold to functional forms which indicates that the fragment can be considered as an independent unit of folding as well.
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PMID:ATP binding to a protease-resistant core of actin. 13 74

Skeletal muscles of flight rats showed no changes in the content of glycogen, adenosine triphosphatase activity of myosin and protein content in protein fractions (except the T fraction where the protein content increased on the 1st and returned to the normal on the 26th postflight day). On the 1st postflight day activities of aminotransferases and lactate dehydrogenase of sarcoplasmatic proteins were elevated and the isoenzyme spectrum of LDH was changed as if in muscular atrophy. The amount of free amino acids in muscles was lowered. On the 26 the postflight day the enzymic activity of sarcoplasmatic proteins remained increased whereas the isoenzyme spectrum of LDH returned to the normal and the amount of free amino acids grew significantly. In the microsomal fraction of muscles the phospholipid content decreased on the 1st and returned to the normal on the 26th postflight day.
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PMID:[Effect of a 22-day space flight on the metabolism of rat skeletal muscle tissue]. 13 80

The kinetics of the Mg2+-dependent ATPase (adenosine triphosphatase) activity of bovine cardiac myosin and its papain subfragment-1 were studied by using steady-state and pre-steady-state techniques, and results were compared with published values for the corresponding processes in the ATPase mechanism of rabbit skeletal-muscle myosin subfragment-1. The catalytic-centreactivity for cardiac subfragment-1 is 0.019s-1, which is less than one-third of that determined for the rabbit protein. The ATP-induced isomerization process, measured from enhancement of protein fluorescence on substrate binding, is similarly decreased in rate, as is also the isomerization process associated with ADP release. However, the equilibrium constant for ATP cleavage, measured by quenched-flow by using [gamma-32P]ATP, shows little difference in the two species. Other experiments were carried out to investigate the rate of association of actin with subfragment-1 by light-scattering changes and also the rate of dissociation of the complex by ATP. The dissociation rate increases with increasing substrate concentration, to a maximum at high ATP concentrations, with a rate constant of about 2000s-1. It appears that isomerization processes which may involve conformational changes have substantially lower rate constants for the cardiac proteins, whereas equilibrium constants for substrate binding and cleavage are not significantly different. These differences may be related to the functional properties of these myosins in their different muscle types. Kinetic heterogeneity has been detected in both steady-state and transient processes, and this is discussed in relation to the apparent chemical homogeneity of cardiac myosin.
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PMID:The magnesium-ion-dependent adenosine triphosphatase of bovine cardiac Myosin and its subfragment-1. 13 61

The masseter muscles of different mammals were studied by means of hisotchemical reactions: NADH: Nitro BT oxidoreductase (NADHOX), 3-hydroxybutyrate: NAD+ oxidoreductase (HBOX), glycerol-3-phosphate: menadione oxidoreductase (GPOX), and acid-stable and alkali-stable myosin adenosine triphosphatase (ATPase). The masseter mucles of cattle and sheep consisted only of the fibres that reacted moderately for GPOX and strongly for NADHOX, HBOX, and the acid-stable ATPase. The masseter fibres of rats and guinea pigs reacted uniformly and strongly for GPOX and the alkali-stable ATPase. The fibres of the rats showed a weak to strong reaction for NADHOX and mostly a negative reaction for HBOX, whereas those of the guinea pigs reacted uniformly and strongly for NADHOX and HBOX.The masseter fibres of swine and dogs showed a weak or strong reaction for the alkali-stable and a negative or weak reation for HBOX. The fibres of the swine were weak to strong in NADHOX activity and those of the dogs uniformly strong; the fibres of the two species gave a moderate to strong reaction for GPOX. The masseter fibres of the ruminant differed from those of the other species in histochemical properties, and appeared to have the histochemical characteristics that meed functional demands for slow, long-term exercise.
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PMID:A comparative histochemical study of the masseter muscle of the cattle, sheep, swine, dog, guinea pig, and rat. 13 87

In the present investigation the results of a lead salt technique and two calcium salt techniques for the deomonstration of the activity of myosin adenosine triphosphatase in sections of both normal and pathological human skeletal muscle specimens are compared. It was seen that the histochemical results obtained by the different techniques are similar, especially with regard to the identification of fibre-types. It can be clearly stated, that the alkaline phosphatase activity present in muscle fibers of diseased skeletal msucles revealed only a very slight activity with the substrate ATP, so the alkaline phosphatase activity in general did not disturb the reliability of the different myosin ATPase techniques. Moreover it was found that the presence of the mitochondrial Ca2+ -ion activated ATPase with a high pH-optimum in muscle fibers did not give rise to faulty results. From studies with dinitrophenol it can be concluded that this substance activates the myosin ATPase present in type I fibres especially.
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PMID:The value of enzyme histochemical techniques in the classification of fibre types of human skeletal muscle. 2. The histochemical demonstration of myosin adenosine triphosphatase in skeletal muscles from adult patients with or with no diseases of the neuromuscular system. A comparison between results obtained by calcium salt and lead salt techniques. 14 Aug 52

Ca2+ regulation of arthropod actomyosin adenosine triphosphatase is associated with both the thin filaments, as in vertebrates, and with the myosin, as in molluscs. The actomyosin of decapod-crustacean fast muscles was previously considered to be an exception, displaying only a Ca2+-regulatory system linked to the thin filaments and not a myosin-linked regulatory system. In the present study, myosin regulation is demonstrated in a variety of decapod muscles when they are tested under more physiological ionic conditions. Myosin regulation is shown by using mixtures of pure rabbit actin with myofibrils, with actomyosin and with purified myosin, and in each case the adenosine triphosphatase is Ca2+ dependent. Myosin regulation may also occur in vertebrate striated muscle, but seemingly is lost during purification of the myosin.
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PMID:Calcium ion-dependent myosin from decapod-crustacean muscles. 14 Dec 78

1. Primary heart cell cultures from neonatal hamsters yielded a heterogeneous cell population, containing muscle cells undergoing progressive differentiation, as well as non-muscle cells. 2. Addition of 5-bromo-2'-deoxyuridine, at an early stage, to such cultures enhanced the formation of beating sheets of differentiated muscle cells. Accumulation of myosin heavy chains and creatine kinase also occurred in the presence of the analogue. 3. To obtain these effects, the analogue had to be added during the initial rapid growth phase of the cells. Division of the treated cells then ceased when the cell numbers had approximately doubled. 4. Similar results were obtained with other inhibitors of DNA synthesis. Thus improved muscle cell cultures can be obtained by preventing non-muscle cells from overgrowing the cultures. 5. One effect caused only by 5-bromo-2'-deoxyuridine was a large increase in the Ca2+-stimulated ATPase (adenosine triphosphatase) activity which sedimented at low ionic strength. This increase was not due to a greater content of myofibrillar myosin, or to myosin isoenzyme changes, because purified myosin prepared from treated and untreated cultures did not exhibit the increased Ca2+-stimulated ATPase activity.
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PMID:Effects of 5-bromo-2'-deoxyuridine on beating heart cell cultures from neonatal hamsters. 14 80

Ca2+ regulation of molluscan actomyosin adenosine triphosphatase is known to be associated with the myosin molecule. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, however, also suggests the possible presence of troponin, a thin-filament-linked Ca2+-regulatory complex. In the present study, scallop troponin and tropomyosin were prepared and complexed with rabbit actin; the resulting synthetic thin filaments form a Ca2+-dependent actomyosin adenosine triphosphatase with Ca2+-insensitive rabbit myosin, indicating that the troponin in scallops is potentially functional. Scallop troponin I was isolated and mixed with chicken troponin C and troponin T, forming a functional hybrid troponin complex, indicating that scallop and vertebrate troponins may act by a common mechanism. Densitometry of sodium dodecyl sulphate/polyacrylamide gels reveals that in synthetic thin filaments there are larger amounts of troponin than are present in native thin filaments. Amounts present in the intact muscle were not determined.
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PMID:Troponin-like proteins from muscles of the scallop, Aequipecten irradians. 14 88


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