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)

Purified skeletal muscle myosin (EC 3.6.1.3) has been covalently bound to Sepharose 4B by the cyanogen bromide procedure. The resulting complex, Sepharose-Myosin, possesses adenosine triphosphatase activity and is relatively stable for long periods of time. Under optimal binding conditions, approximately 33% of the specific ATPase activity of the bound myosin is retained. Polyacrylamide gel electrophoresis of polypeptides released from denatured Sepharose-Myosin indicates that 85% of the myosin is attached to the agarose beads through the heavy chains and the remainder through the light chains, in agreement with predictions of binding and release based upon either the lysine contents or molecular weights of themyosin subunits. The adenosine triphosphatase of the immobilized myosin has been investigated under conditions of varying pH, ionic strength, and cation concentration. The ATPase profiles of immobilized myosin are quite similar to those for free myosin, however subtle differences are found. The Sepharose-Myosin ATPase is not as sensitive as myosin to alterations in salt concentration and the apparent KM is approximately two-fold higher than that of myosin. These differences are probably due to chemical modification in the region of the attachment site(s) to the agarose beads and hydration and diffusion limitations imposed by the polymeric agarose matrix.
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PMID:Preparation and characterization of an enzymatically active immobilized derivative of myosin. 0 72

TTP accelerated ATP-induced superprecipitation of actomyosin in as low a concentration as 30 muM and decreased light scattering by actomyosin. These effects could also be observed in the same way, but to a lesser degree, by addition to TDP. Myosin was able to hydrolyze TTP to TDP, but some important differences were confirmed between myosin TTPase and ATPase. Myosin TTPase was inhibited by actin and showed a much larger Km than that of ATPase. TTP significantly inhibited myosin B ATPase and ATP greatly inhibited myosin B TTPase. These findings suggest that the accelerating effect of TDP and TTP may be due to the binding of thiamine phosphate to the regulatory site of myosin followed by a change in its physical chemical property, rather than due to the competitive binding of thiamine phosphate to the catalytically activity site of myosin.
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PMID:Thiamine triphosphatase activity of myosin and accelerating effect of thiamine di- and tri-phosphates on superprecipitation of actomyosin. 0 81

Cardiac myosin from thyrotoxic animals (myosin-T) exhibits elevated Ca2+ -ATPase activity which is resistant to further stimulation by sulfhydryl modification. In the present study, we have compared the enzymatic properties of myosin-T with those of myosin from euthyroid rabbits (myosin-N) and the derivatives of myosin-T and myosin-N formed by blocking the most rapidly reacting class of thiols (SH1) with N-ethylmaleimide (NEM). Vmax for Ca2+ -ATPase of myosin-T was about 250% greater than myosin-N and was nearly the same as NEM-modified myosin-N. Values for the apparent Km of myosin-T and NEM-modified myosin-N were 200% greater than the value for unmodified myosin-N. Vmax and Km for K+ (EDTA)-ATPase activity of NEM-modified myosin-T and myosin-N were identical. The Ca2+ saturation, pH, and salt-dependency curves for the ATPase activity of myosin-T were parallel to the curves for myosin-N and differed from those for the NEM-modified myosins. Myosin-T exhibited an increased rate of hydrolysis of ATP, CTP, and UTP in both low (0.05m) and high (0.5m) KCl medium. NEM-modified myosin-N showed increased hydrolysis of ATP and CTP in low KCl medium and increased hydrolysis of ATP, CTP, and UTP in high KCl medium. These results support the hypothesis that the enzymatic behavior of myosin-T may be caused by an alteration in the active site near the SH, thiols. The unique enzymatic properties of myosin-T did not seem to be the result of a major change in structure. The electrophoretic pattern of light chains from myosin-T and myosin-N was the same in polyacrylamide gels containing either 8 M urea at pH 8.6 or sodium dodecyl sulfate. Also, myosin-T had a normal amino acid composition and lacked 3-methyl-histidine and hot acid-stable phosphate.
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PMID:Enzymatic properties of native and N-ethylmaleimide-modified cardiac myosin from normal and thyrotoxic rabbits. 0 19

Myosin was extracted and partially purified from the head portion of spermatozoa of the starfish, Asterias amurensis. The sperm myosin showed a specific Ca2+-activated ATPase [EC 3.6.1.3] activity of 0.2 mumoles Pi/min/mg at high ionic strength and pH 6.5. It resembled egg myosin in forming thick filaments, becoming attached to actin filaments. subunit composition, and serological properties.
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PMID:Isolation of myosin from starfish sperm heads. 1 47

Myosin from rabbit stomach was highly purified by ammonium sulfate fractionation in the presence of ATP and MgCl2, ultracentrifugation and Sepharose 4B chromatography. The myosin composed of one heavy and two light chains as determined by SDS-gel electrophoresis. The molecular weights of the light chains were the same as those of gizzard myosin, about 20,000 and 17,000, respectively. The pH-activity curve and the KCl concentration dependency of Ca-ATPase of the stomach myosin were similar to those of other smooth muscle myosins. The stomach myosin was more resistant to pepsin digestion than skeletal myosin. Other proteolytic enzymes, trypsin, chymotrypsin, papain, and nagarse, digested the myosin in the same way as skeletal myosin.
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PMID:Purification and some properties of rabbit stomach myosin. 1 37

For the histochemical demosntration of the Myosin-ATPase (EC 3.6.1.3) the pH of both the preincubation and the incubation medium was varied in steps of 1 within a range: 10.2 to 10.5 and 9.3 to 9.9, respectively. The optimum combinations of both pH values, defined as the ones providing most consistent contrast among the three major types of muscle fibers were determined in 9 different muscles of the rat. The spectrum of optimum combinations differs considerably from muscle to muscle. The reduction of the incubation pH by only 0.1 may drastically change the staining pattern. This probably reflects the unspecificity of the histochemical procedure as well as the plasticity of the ATPase systems. To cope with the lability of the myosin-ATPase the optimum pH values of both media should be determined for each muscle separately.
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PMID:Variable pH dependence of the myosin-ATPase in different muscles of the rat. 3 7

An immunocytochemical approach was used to localize myosin with respect to individual fibers in rat skeletal muscle. Transverse cryostat sections of rat diaphragm, a fast-twitch muscle, were exposed to fluorescein-labeled immunoglobulin against purified chicken pectoralis myosin. Fluorescence microscopy revealed a differential response among fiber types, identified on the basis of mitochondrial content. All white and intermediate fiber but only about half of the red fiber reacted with his antimyosin. In addition, an alkali-stable ATPase had the same pattern of distribution among fibers, which is consistent with the existence of two categories of red fibers. The positive response of certain red fibers indicates either that their myosin has antigenic determinants in common with "white" myosin, or that the immunogen contained a "red" myosin. Myosin, extracted from a small region of the pectorlis which consists entirely of white fibers, was used to prepare an immunoadsorbent column to isolate antibodies specific for white myosin. This purified anti-white myosin reacted with the same fibers of the rat diaphragm that had reacted with the white, intermediate, and some red fibers are sufficiently homologous to share antigenic determinants. In a slow-twitch muscle, the soleus, only a minority of the fiber reacted with antipectoralis myosin. The majority failed to respond; hence, they are not equivalent to intermediate fibers of the diaphragm; despite their intermediate mitochondrial content. Immunocytochemical analysis of two different musles of the rat has demonstrated that more than one isoenzyme of myosin can exist in a single muscle, and that individual fiber types can be recognized by immunological differences in their myosin. We conclude that, in the rat diaphragm, there are at least two immunochemically distinct types of myosin and four types of muscle fibers: white, intermediate, and two red. We suggest that these fibers correspond to the four types of motor units described by Burke et al. (Burke, R. E., D. N. Levine, P. Tsairis, and F. E. Zajac, III 1973. J. Physiol. (Lond) 234:723-748.)in the cat gastrocnemius.;
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PMID:Polymorphism of myosin among skeletal muscle fiber types. 7 2

Myosin A and actomyosin were isolated from the skeletal muscle of old and young rats. The velocity of the Ca2+ activated myosin A ATPase was increased in the case of the older animals. On the other hand the velocity of the Mg-2plus activated actomyosin ATPase was decreased in the skeletal muscle of the aging rats. At 5 X 10-5M EGTA concentration the inhibition of the Mg-2plus activated myosin B ATPase of the 1-month-old rats was two- to threefold smaller than that of the older animals. It was shown that the myosin A component of the actomyosin was responsible for the decreased troponin inhibition in the case of the 1-month-old rats. Between the ages of 1 month and 29 months the number of free myosin A SH groups decreases by 50%. The lipid peroxidation in the muscle of the 1-month-old animals.
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PMID:Enzymatic studies on the skeletal myosin A and actomyosin of aging rats. 12 7

Myosin and its active subfragments were trinitrophenylated under conditions in which mainly the active site(s) was modified. Proteins modified at the active site(s) could be separated by affinity chromatography on agarose-ATP columns. By two independent methods, ATPase activity measurements and analysis of elution patterns on agarose-ATP columns, it was shown that the introduction of two trinitrophenyl groups per myosin or one per heavy meromyosin subfragment 1 molecule is responsible for the remarkable change in the ATPase activities. Heavy meromyosin subfragment 1 prepared from trinitrophenylated myosin retained the original degree of trinitrophenylation per "active head." The kinetic constant of trinitrophenylation of the epsilon-amino group of lysine at the active site was found to be 2000 S-1-M-1, whereas a much smaller constant of 2.2 S-1-M-1 was obtained for the trinitrophenylation of the unessential lysyl residues of myosin. By using affinity chromatography, we could follow the formation of mono- and ditrinitrophenyl myosin. The amounts of these myosin derivatives at various extents of the reaction corresponded approximately to the calculated amounts, assuming a random and independent trinitrophenylation of the two myosin "heads." It is concluded that in each of the two heads of myosin there is one ATPase active site and these two sites behave in an identical manner with respect to trinitrophenylation.
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PMID:Identical behavior of the two active sites of myosin with respect to trinitrophenylation. 12 28

Myosin was isolated from leucocytes in horse arterial blood by the same procedures used for the isolation of myosin from skeletal muscle. The Ca2+-, EDTA-, and Mg2+-ATPase [EC 3.6.1.3] activities of the protein was 0.148, 0.147, and 0.001 mumoles/min/mg, respectively, in 0.5 M KCl at pH 7.0 and 25 degrees. The Ca2+-ATPase activity decreased with decrease in the ionic strength. No difference was found between leucocyte myosin and skeletal myosin in the pH profiles of Ca2+- and EDTA-ATPases. The rate and amount of the initial burst of Pi liberation of leucocyte myosin were 0.002 mumoles/min/mg and 0.83 moles/4.8 X 10(5)g, respectively. Leucocyte myosin aggregated into filaments of 0.3 mum length and 150 A diameter, which had a bare shaft and irregular projections. At high ionic strength, the protein bound to skeletal muscle F-actin to form a complex with the characteristic arrowhead structure.
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PMID:ATPase activity and filament formation of partially purified myosin from leucocytes. 12 90


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