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:3.6.4.1 (myosin ATPase)
1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies were conducted to examine the effects of chronic adrenalectomy (Adx) and adrenalectomy plus glucocorticoid replacement therapy on rat cardiac contractile protein ATPase activities. The Ca2+-dependent Mg-ATPase activity of myofibrils isolated from rat ventricles 3 weeks postadrenalectomy (Adx) was significantly decreased at all pCa2+ concentrations (P less than 0.01), compared to sham-operated (SO) rats. Similarly, Ca2+-, K+-EDTA, and actin-activated myosin ATPase activities of Adx rat hearts were markedly decreased below that of SO rats (P less than 0.01). Dexamethasone administration to Adx rats prevented the decrease of Ca2+- and K+-ATPase activities of myosin, but not of myofibrillar Ca2+-dependent Mg-ATPase or actin-activated myosin Mg-ATPase activities. These studies suggest that glucocorticoid insufficiency induced by adrenalectomy results in altered myocardial contractile protein ATPase activity which may underlie impaired cardiac performance.
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PMID:Changes in myocardial contractile protein ATPases in chronically adrenalectomized rats with and without glucocorticoid replacement. 252 74

A substance which inhibits the myosin ATPase has been detected from an Okinawan marine sponge. The inhibitor has been isolated from the methanol-soluble extract of the sponge by gel filtration and hydrophobic chromatography. The isolated inhibitor is an amphipathic peptide, which is rich in Asp, Glu, Ser, and Gly, and devoid of Met and Trp. The molecular weight of the peptide is about 6300 as determined by gel filtration, amino acid analysis, and sodium dodecyl sulfate-gel electrophoresis. The peptide is a potent inhibitor not only for the K+-, Ca2+-, and Mg2+-ATPases of myosin, its subfragment-1, and actomyosin, but also for superprecipitation of actomyosin, inhibiting them completely in the range of 10-400 ng/ml. The peptide inhibitor may provide a useful tool to elucidate the structure-function relationship of the myosin ATPase.
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PMID:A novel peptide inhibitor of the myosin ATPase from an Okinawan marine sponge. 253 Feb 20

The heavy chain of myosin from rabbit skeletal muscle can be cleaved at three sites by irradiation with near-ultraviolet light in the presence of 0.1-1.0 mM vanadate. The sigmoidal dependence upon vanadate concentration, with half-maximal rate occurring at about 0.5 mM vanadate and a sigmoidicity of 2.7, is consistent with the chromophore responsible for cleavage being oligomeric vanadate. Cleavage occurs at two sites located within the head region of the molecule, 23 kDa and 75 kDa from the NH2-terminus; these sites are cleaved equally well in heavy meromyosin and subfragment 1. In the presence of 1 mM vanadate, the half-times for cleavage of the 23-kDa and 75-kDa sites are about 15 and 10 min, respectively. The rate of cleavage at both these sites is retarded 2-3-fold by the presence of greater than 10 microM MgATP. The third photocleavage site is located about 5-10 kDa from the COOH terminus of the intact heavy chain, and cleaves equally well in the isolated rod and in light meromyosin. Cleavage at this site occurs with a half-time of 138 min, and its rate is unaffected by the presence of MgATP. The vanadate-mediated cleavage of the heavy chains is accompanied by characteristic changes in the myosin ATPase properties, with the Ca2+, Mg2+ and actin-activated Mg2+ ATPases becoming elevated, whereas the K+/EDTA ATPase becomes inactivated. The sites of photocleavage in the myosin heavy chain might be associated with sites of phosphate binding.
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PMID:Vanadate-mediated photocleavage of rabbit skeletal myosin. 253 8

N-Ethyl-maleimide (NEM, 2.5 x 10(-5) M) inhibited the compound action potential of the phrenic nerve and increased the spontaneous release of transmitter from the nerve terminals, recorded as miniature endplate potentials. The first effect was the cause of a blockade of the phrenic nerve diaphragm preparation, during indirect stimulation. The left phrenic nerve was more susceptible to inhibition than the right. An increase of the threshold was observed during the progression of the inhibition. The inhibition was not use-dependent and there was no synergistic interaction with the local anaesthetic drug, tetracaine. The inhibition was partly antagonized by di-thio-threitol (3.0 x 10(-3) M). The increase of spontaneous release of transmitter was not accompanied by an increase of the stimulus-evoked release since the amplitude of the endplate potential was not increased and partial inhibition caused by d-tubocurarine or magnesium chloride was not antagonized. When the concentration of NEM was increased to 2.75 x 10(-4) M, the directly-elicited twitches were inhibited, and the baseline tension was increased. This increase of tension was slightly reduced in a preparation depolarized with potassium chloride; a small depolarization could partly explain this effect. It was not reduced by dantrolene or in a calcium-free solution. The inhibition of the twitch and the increased baseline tension (probably a rigor) might be caused by a reduced sensitivity of the contractile proteins for calcium ions and an inhibition of the myosin ATPase activity, respectively.
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PMID:Effects of the sulphydryl inhibitor N-ethyl-maleimide on the phrenic nerve and diaphragm muscle of the rat. 257 Nov

The pathogenesis of reduced systolic left ventricular function in dilated cardiomyopathy is yet unclear. To analyze a possible involvement of contractile protein, function and structure of left ventricular myofibrils were examined in hearts of patients with advanced cardiomyopathy undergoing heart transplantation and in normal control hearts (from renal transplant donors). Myosin and actin content of the left ventricular myocardium was slightly reduced in cardiomyopathic hearts. Myofibrillar polypeptide composition was determined using two-dimensional electrophoresis and immunoblotting. No differences in constituting polypeptides were apparent, including Z-line proteins and proteins of the endosarcomeric lattice. M-line-bound creatine kinase was identical in both groups. Further, basal and maximal myofibrillar adenosine triphosphatase (ATPase) activities were unaltered in dilated cardiomyopathy. The structure of purified myosin was identical in both groups by the following criteria: electrophoretic mobility of native myosin, identical pattern of light chains after isoelectric focusing, identical cleavage peptides of myosin's heavy chain, and identical patterns after immunoblotting of heavy chain cleavage peptides using polyclonal antibodies generated against myosin from normal and cardiomyopathic ventricles. Ca2+-activated, K+-EDTA-activated and actin-activated myosin ATPase activities were identical in control and cardiomyopathic hearts. A structural alteration or functional defect of myofibrils does not seem to be primarily involved in the pathogenesis of reduced myocardial contractility in dilated cardiomyopathy.
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PMID:Structure and function of contractile proteins in human dilated cardiomyopathy. 258 58

The role of motor innervation and muscle tension in the posthatching maturation of the slow-tonic anterior latissimus dorsi (ALD) muscle of the chicken has been investigated. Modification of the muscle tension was obtained either by maintaining ALD in a shortened state or by stretching, after or without denervation. In denervated as well as in innervated ALD, shortening resulted in atrophy and inhibition of developmental change in muscle fiber population. In contrast, stretch causes hypertrophy, transformation of all 3B fibers, increase in SM2 isomyosin expression, and decrease in Ca2+-activated myosin ATPase in innervated or denervated ALD. On the other hand oxidative activity in ALD fibers was strikingly reduced after denervation even in presence of stretch-induced hypertrophy. This study suggests that a passive stretch can be involved in some, but not all, changes in ALD characteristics occurring after denervation and may be also involved in normal posthatching development of the slow-tonic muscle. Possible clinical implications of these results in relation to treatments for preventing muscle atrophy resulting from immobilization or disuse are suggested.
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PMID:Role of nerve and tension in maturation of posthatching slow-tonic muscle in chicken. 260 90

Myosin (opaque myosin) isolated from the opaque portion of scallop smooth muscle, a catch muscle, was subjected to limited digestion by trypsin during the steady-state ATPase reaction. The 200-kDa heavy chain of opaque myosin was cleaved into 125- and 74-kDa fragments. The proteolytic rate in the absence of Ca2+ was lower than that in the presence of Ca2+, and was similar to that in the presence of ADP and absence of Ca2+. The results suggest that the steady-state intermediate of opaque myosin ATPase in the absence of Ca2+ is EADP, which is consistent with the previous results based on the difference UV-absorption spectrum (Takahashi, M., Sohma, H., & Morita, F. (1988) J. Biochem. 104, 102-107). In the presence of F-actin, the proteolytic rates were decreased, but the digestive patterns by trypsin were similar to those of myosin alone. Even in the presence of F-actin, the proteolytic rate during the ATPase reaction in the absence of Ca2+ was lower than that in the presence of Ca2+, and was similar to that in the presence of ADP and absence of Ca2+. In addition, there was another trypsin-susceptible site which is probably located at 18 kDa from the N-terminal of the heavy chain. The site in the absence of Ca2+ was hardly cleaved when ATP or ADP was present. Similar tendencies were observed even in the presence of F-actin. These findings suggest that the intermediate of opaque myosin ATPase at the steady state in the absence of Ca2+ is EADP even in the presence of F-actin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Myosin may stay in EADP species during the catch contraction in scallop smooth muscle. 261 94

To clarify the mechanisms by which volatile anesthetics may depress myocardial contractility, the depressant effects of equivalent concentrations of isoflurane, enflurane and halothane were compared in rat and frog ventricular myocardium, preparations which differ markedly in excitation-contraction coupling. In Tyrode solution, right ventricular papillary muscles from rat exhibited very large, rapidly developing contractions after rest, with a subsequent negative force-frequency relation as the stimulation rate was increased to 0.1, 0.25, 0.5, 1, 2, and 3 Hz. The large contractions after rest and at 0.1 Hz were depressed by 0.75% halothane and 1.7% enflurane to about 60% of control, but less so by 1.3% isoflurane (approximately 0.8 MAC). Halothane at 1.5% was more depressant than 2.5% isoflurane at all stimulation rates, while 3.5% enflurane caused intermediate depression (approximately 1.6 MAC). Contractions in frog ventricular strips were studied in Ringer solution following rest and at stimulation rates of 0.1, 0.25, 0.5, and 1 Hz, in the absence and presence of equivalent anesthetic concentrations. At 0.1 to 1 Hz, isoflurane was less depressant than equivalent concentrations of halothane. Enflurane (1.7%) was less depressant than 0.75% halothane at 0.1 and 0.25 Hz; 3.5% enflurane was more depressant than 2.5% isoflurane at 1 Hz. Anesthetic effects on sustained contractures were also studied in frog ventricular strips that were superfused for 4-5 min with 40, 60, 80, and 100 mM K Ringer solution. Contractures induced by 80 and 100 mM K solution were depressed more by halothane (to 60% of control) than by isoflurane or enflurane (approximately 85% of control). However, only enflurane depressed the contractions at 1 Hz more than the sustained contractures in 100 mM K Ringer. The Ca2+ for activating contractions in rat ventricle is derived largely from the sarcoplasmic reticulum, the intracellular Ca2+ accumulation and release organelle. In contrast, Ca2+ for activating contractions in the frog ventricle originates primarily from the external medium. These results suggest that halothane is more potent than isoflurane in reducing the amount of Ca2+ rapidly released from the sarcoplasmic reticulum (as observed in rat), as well as in depressing entry of extracellular Ca2+ to activate myofibrils (as in frog). Enflurane appears to have intermediate potency with actions distinct from halothane and isoflurane. The greater potency of halothane may also be due in part to greater direct depression of actin-myosin ATPase.
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PMID:Depressant effects of volatile anesthetics upon rat and amphibian ventricular myocardium: insights into anesthetic mechanisms of action. 278 93

Calcium-independent regulation of the contractile proteins of cardiac muscle has been studied using hyperpermeable cells from rat ventricles and sections of quickly-frozen rat hearts. These preparations have been used to study maximum Ca-activated force, myosin ATPase activity and the maximum velocity of unloaded shortening. Beta adrenergic activity increases the amount of force and the ATPase activity in accordance with the concentration of the V1 isozyme of myosin. V3 activity is decreased at the same time. In tissues containing only V1, there is no change in maximum velocity in response to beta adrenergic stimulation. These results indicate that beta adrenergic stimulation recruits V1 force generators and probably regulates the transition between a Ca unresponsive and a Ca responsive force generator. This type of regulation provides the cell with the ability to operate along many different force-velocity relations.
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PMID:Ca-independent regulation of cardiac myosin. 282 83

The effects of Cd2+ on Ca2+-sensitive myosin ATPase activity were examined. In the absence of Ca2+, the Ca2+-dependent myosin ATPase activity was enhanced by Cd2+ to the same extent as with Ca2+ at concentrations ranging from 10(-6) to 10(-3) M. At 10(-2) M, however, no activation was observed. Zn2+, Co2+, and Sr2+ also activated the myosin ATPase. Sr2+ and Co2+ were less effective. Hg2+, Cr3+, and Cu2+ were essentially inactive. In the presence of below 10(-3) M Ca2+, the increase in the enzyme activity observed on the addition of Cd2+ was in addition to that caused by Ca2+ alone. The ability of metal ions to activate myosin ATPase was compared with that to activate calmodulin-dependent cAMP phosphodiesterase. The activating effects of the metal ions tested were in the order of Ca2+ greater than Cd2+ greater than Zn2+ greater than Co2+ greater than Sr2+ for Ca2+-sensitive myosin ATPase and Ca2+ greater than Cd2+ greater than Sr2+ greater than Zn2+ greater than Hg2+ greater than Co2+ for cAMP phosphodiesterase. Cd2+ activated both enzyme activities most efficiently among the metal ions tested except Ca2+. These results indicate that Cd2+ is able to substitute for Ca2+ in the case of Ca2+ dependent enzymes, regardless of whether or not calmodulin participates in the activating process.
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PMID:Enhancement of Ca2+-sensitive myosin ATPase activity by cadmium. 282 3


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