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)

Myosin was isolated from the smooth muscles of small intestine of calf with good yield and its properties were compared with the myosin's properties from the skeletal rabbit muscle. The crude myosin was purified by means of DEAE-cellulose column chromatography, using a KCl gradient. The purity of the preparations was checked spectrophotometrically by the densities of adsorption D280/D260, viscosimmetrically by the sensitivity to ATP, electrophoretically and by ultracentrifugation. By the above-mentioned properties the smooth muscle myosin was similar to the high-purified skeletal muscle myosin. A comparative study of the enzymatic properties of myosin from two types of tissues, showed the following differences: (1) in the dependence the Ca2+-ATPase activity on the KCl concentration in the incubation medium; (2) in the degree of myosin activation by actin in the presence of Mg2+; (3) in the behaviour of Ca2+-ATPase dependence on pH; (4) the different temperature optima of the ATPase activity.
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PMID:[Preparation and the properties of a highly purified preparation of myosin from smooth muscles]. 13 28

Myosin was isolated from cultured human endothelial cells by extraction with 0.6 M KCl and chromatography on Sepharose 4B. The extracted endothelial cell protein was identified as myosin by the characteristic ATPase profile, that is, the ATPase was activated by Ca2 + and EDTA and inhibited by Mg2 +. On sodium dodecyl sulphate polyacrylamide gel electrophoresis, the endothelial cell myosin heavy chain migrated with a molecular weight of 200 000 as did rabbit uterine and human platelet myosin heavy chains. A crude preparation of the endothelial cell myosin reacted immunologically with an antiserum to platelet myosin, a smooth muscle type of myosin. In indirect immunofluorescence studies, antiserum to the purified endothelial cell myosin stained cultured endothelial cells in a fibrillar pattern. The fibrillar pattern was more intense when the endothelial cells were stained with antiserum to platelet myosin. The presence of myosin in the endothelial cell provides a basis for the contractility of these cells. This contractile property may plan an important role in the physiologic function of these cells.
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PMID:Myosin in cultured human endothelial cells. 13 15

Lipase activity extracted from cultured neonatal rat heart cells was characterized and identified as lipoprotein lipase. Enzyme activity was stimulated by human apoC-II and rat serum; serum stimulation was prevented by human apoC-I and by apoC-II. Lipolysis was maximal at pH 8.0 and was inhibited by protamine sulfate, NaCl, and high concentrations of heparin. About 50% of heart cell lipase activity applied to heparin-Sepharose bound to the gel and was eluted with a NaCl gradient. A peak of lipase activity was observed at 0.84 M NaCl. Neonatal rat heart cells in culture are a mixture of muscle and non-muscle cells. To determine the cellular location of the lipoprotein lipase, enzyme activity and muscle cell content of the cultures were determined. Myosin ATPase was used as an index of muscle cell content since ATPase specific activity correlated (r = +0.97) with muscle cell content determined immunofluorescently. When muscle cell content of cultures was decreased or increased by differential plating, lipase specific activity was constant. Moreover, lipase specific activity was constant during culture growth despite a decrease in muscle cell content. It was concluded that lipoprotein lipase activity of cultured heart cells is not associated solely with either muscle or non-muslce cells.
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PMID:Lipoprotein lipase in cultured heart cells: characteristics and cellular location. 13 38

Myosin and paramyosin have been purified from the nematode, Caenorhabditis elegans. The properties of the myosin in general resemble those of other myosins. The native molecule is a dimer of heavy (210,000 dalton) polypeptide chains and contains 18,000 and 16,000 dalton light chains. When rapidly precipitated from solution, it forms small, bipolar aggregates, about 150 nm long, consistent with the expected molecular structure of a rigid rod with a globular head region at one end. Its ATPase activity is stimulated by Ca2+ and EDTA. The myosin binds to F actin in a polar and ATP-sensitive manner, and the Mg2+-ATPase is activated by either F actin or nematode thin filaments. Dialysis of myosin to low ionic strength produces very long filaments. When a myosin-paramyosin mixture is dialyzed under the same condtions, co-filaments form which consist of a myosin cortex, surrounding a paramyosin core. Some properties of myosin from the mutants E675 and E190, which have functionally and structurally altered body wall muscles, are compared with those of wild-type myosin. These myosins of these results are discussed in terms of the myosin heavy chain composition.
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PMID:Myosin and paramyosin of Caenorhabditis elegans: biochemical and structural properties of wild-type and mutant proteins. 14 Jul 64

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

CA2+-ATPase activity and light chains of myosin prepared from fast and slow muscles of rat guinea-pig and rabbit were studied during development from embryonic to old age to establish further correlation with the well-known developmental changes in contraction properties of these muscles. The changes involve the slow soleus muscle much more than the fast extensor digitorum longus muscle. Myosin-ATPase activity of the soleus muscle before or at birth is higher than in the muscle of adult animals. Myosin from the soleus muscle of embryos or newborn animals reveals light chains of myosin of both fast and slow type (with a preponderance of light chains of fast type in 26-days-old rabbit embryos). During postnatal development the amount of light chains of the fast type decreases, that of the slow type increases. Myosin from the soleus muscle of adult animals contains only light chains of the slow type. However, myosin from the soleus muscle of 30-months-old rats exhibits high myosin ATPase activity and contains light chains of myosin of both slow and fast type as in perinatal development. This is in agreement with the shortening of contraction time observed in this muscle in very old age. Thus developmental differentiation of myosine in the soleus muscle is followed by a trend of levelling out of the differences between fast and slow muscles of senescent animals. No such "biphasic" development is observed with respect to the fast extensor digitorum longus muscle.
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PMID:Differentiation of myosin in soleus and extensor digitorum longus muscle in differnt animal species during development. 14 53

Myosin was incubated with a large excess of exogenous g1, g2 or g3 in 0.6 M KSCN (or in 4 M LiCl) for 1-2 h at 0-2 degrees C. KSCN (or LiCl) was then removed by dialysis. The composition of g-chains in the resulting myosin was analyzed by SDS-gel electrophoresis. When myosin was incubated with g1, the amount of g1 in myosin increased and the increment was nearly counterbalanced by a decrease in g3, whereas an opposite change was observed on incubation with g3. The amount of g2 was not changed by these treatments. The same ATPase activity as that of control myosin was observed in the presence of Ca2+ or EDTA with the myosins incubated with g1, g2, or g3, but the activity in the presence of Mg2+ was about one-half of the control. The Ca2+ sensitivity of actomyosin containing the treated myosins was slightly higher than that of actomyosin containing the control myosin. Spin-labeled g1 or spin-labeled g3 was incorporated into myosin, but the ESR spectra of two spin labels were not distinguishable. No information could be obtained from the ESR spectra by the addition of Ca2+, Mg2+, nucleotides or actin. Inhibition of ATPase activity was observed when SH groups g1 or g3 in myosin were chemically modified.
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PMID:Incubation of myosin with exogenous small components (g1, g2, or g3) in KSCN or LiCl and properties of g-exchanged myosins. 14 65

Myosin from the hearts of thyrotoxic animals (myosin-T) exhibits elevated Ca2+-ATPase activity. To clarify the physiological significance of this increased activity, we have investigated the steady state kinetics of the interaction of actin and MgATP with the double-headed heavy meromyosin subfragment of cardiac myosin from thyrotoxic rabbits (HMM-T). The enhanced Ca2+-ATPase activity of myosin-T was completely retained in HMM-T. The Vmax for actin-activated MgATP hydrolysis by HMM-T (1.08 +/- 0.10 mumol of Pi/mg/min). Under physiological ionic conditions, the Vmax was 0.14 +/- 0.02 mumol of Pi/mg/min as compared with the normal value of 0.08 +/- 0.01 mumol of Pi/mg/min. Furthermore, the salt dependence of Vmax and Kapp for the actin-activated ATPase of HMM-T differed markedly from normal and resembled that usually associated with the single-headed (S1) cleavage product of myosin. These results suggest that the changes in enzymatic properties of myosin-T are responsible for the increased speed of contraction observed in the hearts of thyrotoxic animals. Also, the alteration in the interaction of HMM-T with actin suggests that a loss of cooperativity between the myosin heads may occur.
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PMID:Enzymatic properties of the heavy meromyosin subfragment of cardiac myosin from normal and thyrotoxic rabbits. 14 72

A myosin B-like protein was extracted from the alga Nitella flexilis. SDS-polyacrylamide gel electrophoresis revealed the presence of myosin heavy chain and actin as the main components. At high ionic strength, its ATPase [EC 3.6.1.3] reaction was activated by EDTA or Ca2+ and inhibited by Mg2+. At low ionic strength, superprecipitation was induced by the addition of ATP. Myosin was purified from Nitella myosin B. The molecular weight of the heavy chain of Nitella myosin, estimated by SDS-gel electrophoresis, was slightly higher than that of skeletal muscle myosin. At low ionic strength, Nitella myosin aggregated to form bipolar filaments about 0.2 micron long. At high ionic strength, its ATPase reaction was activated by EDTA or Ca2+, and inhibited by Mg2+. The Mg2+-ATPase reaction of Nitella myosin was activated by skeletal muscle F-actin.
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PMID:Identification of myosin in Nitella flexilis. 14 21

Myosin and subfragment-1 were prepared from rabbit hearts hypertrophied secondary to pulmonary artery constriction. The Ca2+ -stimulated ATPase activity was reduced while the potassium/EDTA-stimulated ATPase activity was unchanged in both the myosin and subfragment 1 (S-1) from hypertrophied hearts. When hypertrophy myosin was mixed with an equal quantity of control myosin, the ATPase activity of the mixed protein fell halfway between control and hypertrophy values. Similar results were obtained with control and hypertrophy S-1. The actin-stimulated ATPase activity of hypertrophy S-1 was slightly depressed but unlike hypertrophy myosin this depression was not significant when compared to normal S-1. This suggests that papain cleavage may have removed part of the conformational difference that exists between control and hypertrophy myosins.
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PMID:The ATPase activity of subfragment-1 from the hypertrophied heart. 14 12


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