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)

70 human hearts were studied less than 36 hours after death. The apex, and in some cases other parts of the myocardium were homogenized, DNA, hydroxyproline content, myofibrillar Ca2+ and Mg2+ ATPase were measured. In normal hearts the DNA and collagen content were 372 +/- 9 mg and 36 +/- 7 mg. Ca2+ and Mg2+ ATPase of the myofibrils prepared from these hearts have shown the same specific activity (35 +/- 5 and 34 +/- 6 nmol/min./mg) as those from fresh biopsies taken during open-chest surgery. The heart weight correlates with the DNA content (r= + 0.58 -p less than 0.01) and with the myofibrillar ATPase (r= - 0.33 - p less than 0.02) but not with the DNA concentration nor with the collagen content or concentration. The main result of this study was the presence of a negative correlation between the DNA content of the heart and the Mg2+ or Ca2+ myofibrillar ATPase (r= - 0.31, p less than 0.05 - r= - 0.45, p less than 0.01). This correlation was analysed with reference to the histological and biochemical studies published by several authors in human or experimental heart hypertrophy and it was suggested that in human heart hypertrophy the decrease of the myofibrillar or myosin ATPase is a direct consequence of the high degree of polyploidy of the muscular cells observed in this condition.
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PMID:Myofibrillar ATPase, DNA and hydroxyproline content of human hypertrophied heart. 13 Feb 42

The effects of D2O on the elementary steps in the contractile and transport ATPase [EC 3.6.1.3] reactions were studied, and the following results were obtained: 1. The rate of H-meromyosin ATPase in the steady state decreased in D2O to 60% of that in H2O. Deuterium oxide did not affect the size or rate of the initial burst of Pi liberation, i.e. the amount or rate of formation of the reactive myosin-phosphate-ADP complex, MADPP. Moreover, neither the rate of change in the fluorescence spectrum of H-meromyosin induced by ATP (the rate of formation of the second enzyme-ATP complex, M2ATP) nor the rate constant of decomposition of MADPP into M degrees + ADP + Pi was affected by D2O. However, the equilibrium constant of the step M2ATP in equilibrium MADPP decreased in D2O to about 1/2 the value in H2O. 2. In the case of the Na+-K+-dependent ATPase reactin, neither the rate constant of formation of the second enzyme-ATP complex, E2ATP, nor that of decomposition of a phosphorylated intermediate, EADP approximately P, was affected by D2O. However, the equilibrium constant of the step E2ATP in equilibrium EADP approximately P decreased in D2O to about 1/2.5-1/4 of the value in H2O. These results suggest a similarity between the modes of binding of phosphate in MADPP in the myosin ATPase reaction and in EADP approximatley P in the Na+-K+-dependent ATPase reaction.
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PMID:Effects of deuterium oxide on elementary steps in the ATPase reaction. Evidence for the similarity of key intermediates in contractile and transport ATPase. 13 92

The interaction between paramyosin and myosin has been studied by enzymological methods. Clam adductor paramyosin inhibits the actin-activated, Mg2+-requiring ATPase of both clam adductor and rabbit skeletal muscle myosins. Myosin and paramyosin must be rapidly coprecipitated for this inhibition. Incubation with F-actin in the absence of ATP does not alter this effect. This inhibition follows a hyperbolic function with respect to paramyosin concentration. Slow precipitation by dialysis of myosin and paramyosin together leads to copolymers with actin-activated ATPase equivalent to that of slowly formed myosin filaments. Both kinds of slowly formed filaments have enzymatic properties distinct from those of the rapidly precipitated proteins. Paramyosin is competitive with F-actin for their effects upon myosin. The apparent affinity of myosin for F-actin is markedly reduced by association with paramyosin, but the extrapolated maximal velocity of actomyosin is unaffected. The specificity of this inhibition is strongly suggested by marked quantitative differences between native and cleaved paramyosins. No inhibition of intrinsic myosin ATPase by paramyosin is seen. These studies suggest that at least two types of condition-dependent association between myosin and paramyosin are possible. One class of interactions is associated with enzymic inhibition in rapidly coprecipitated filaments, whereas slowly formed cofilaments exhibit catalytic activity similar to that of identically treat-d myosin and have a characteristic 14.5 nm axial repeat.
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PMID:Myosin-paramyosin cofilaments: enzymatic interactions with F-actin. 13 57

Ca2+ATPase activity and light chains of myosin, fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, in developing, adult and denervated fast, slow and cardiac muscles of the rat, guinea-pig, cat, rabbit and chick were studied. It has been shown that in normal adult muscles the electrophoretic pattern of light chains of myosin reflects the myosin ATPase activity only when muscles from the same animal species are compared. In homologous muscles from adult animals differing in size, the size-dependent difference in myosin ATPase activity is not revealed in the electrophoretic pattern. Both in developing and in denervated muscle, changes in myosin ATPase activity are either connected with changes in the pattern of light chains of myosin or this pattern does not change. This relation is different in fast and slow muscles and also differs in chick and rabbit muscles. There are several possibilities of explaining the relation between ATPase activity of myosin and the pattern of light chains of myosin. The observation that myosin from the soleus muscle of 1-month-old rabbit contains light chains corresponding to both fast and slow type of myosin, indicates that the change in myosin ATPase activity during development is due to changes in the ratio between the fast and slow type of myosin.
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PMID:The relation between ATPASE activity and light chains of myosin in developing, adult and denervated muscles of several animals species. 13 84

The effects of a moderate physical training program on the hearts of rats have been studied. The mechanical responses of these hearts are improved. Possible contributing factors in this improvement are increased coronary reserve and capacity to deliver oxygen to the myocardium, increased myocardial glycogen stores and increased turnover of fatty acids through the endogenous triglyceride pool. Myocardial oxidative compounds and high energy phosphate stores are not altered. Major changes are found in the energy utilization pathways. Actomyosin, myosin, and heavy meromyosin ATPase activity and binding activity of isolated sarcoplasmic reticulum are all enhanced. Sulfhydryl control of the active site of myosin ATPase is altered. The biochemical effects of conditioning are short lived when training is decreased or discontinued.
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PMID:Effects of physical training and detraining on intrinsic cardiac control mechanisms. 13 72

The effect of 5-hydroxytryptamine (5HT) on the ATPase activity and sulphydryl group reactivity of mammalian skeletal muscle actomyosin has been studied. 5HT inhibited the Mg2+-activated but not the Ca2+-activated ATPase activity of actomyosin. It slightly activated myosin ATPase. The sulphydryl groups of actomyosin reacting with 5,5'-dithiobis-(2-nitrobenzoic acid) were blocked by concentrations of 5HT which inhibited the Mg2+-activated ATPase. The significance of the results are discussed in relation to the muscle lesions in the experimental myopathy induced by 5HT and imipramine.
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PMID:Inhibition of actomyosin ATPase by high concentrations of 5-hydroxytryptamine. Possible basis of lesion in 5HT-induced experimental myopathy. 13 9

Bovine cardiac myosin ATPase activity was rapidly inactivated by the purine disulfide analog of ATP,6,6'-dithiobis(inosinyl imidodiphosphate). Kinetic investigations showed that this analog acted as a site-specific reagent at 0 degrees with a Ki of 130 muM and a half-life of 8.2 min at saturating inhibitor concentrations. Concentrations (50 to 500 muM) of ATP, adenyl-5'-yl imidodiphosphate (AMP-PNP), or ADP that saturated the active site caused an enhancement in the rate of inactivation, indicating the purine disulfide analog was not reacting at the active site. Under these conditions saturation kinetic data were still observed with Ki values remaining unchanged (120 muM) but with the half-life of inactivation decreasing to 6.0 min (ATP) and 4.6 min (AMP-PNP) at saturating inhibitor concentrations. At concentrations greater than 0.5 mM ATP, AMP-PNP, or ADP there was a decrease in the rate of inactivation, implying protection by these nucleotides. However, saturation kinetics of inactivation could no longer be demonstrated, implying a change in the mechanism of inactivation. A comparison of the inactivation of the Mg2+, Ca2+, and EDTA-ATPase activities of cardiac myosin after modification by the purine disulfide analog showed that the Mg2+- and Ca2+ATPase activities plateaued at approximately 60% and 40%, respectively, while the EDTA-ATPase activity continued to decrease to below 10%. This evidence supports the suggestion that the purine disulfide analog was not reacting at the active site. Equilibrium dialysis experiments were used to measure the binding of [8-3H]AMP-PNP to native cardiac myosin, the thiopurine nucleotide-modified myosin, and the derivative formed by displacing the thiopurine nucleotide by cyanide (thiocyanato-myosin). Native myosin bound a total of 2.1 mol of AMP-PNP with a binding constant of 6.0 X 10(6) M-1. There was a 15 to 40% decrease in the number of AMP-PNP binding sites in the enzyme derivatives, but the active sites appeared not to be blocked since the association constants remained essentially unchanged (KA=3.9 X 10(6) M-1 for thiopurine nucleotide-myosin and 12.0 X 10(6) M-1 for thiocyanato-myosin). The kinetic studies and the binding experiments indicate that the purine disulfide analog reacts at a specific site other than the active site but do not offer support to earlier suggestions from skeletal myosin studies that this site is a possible ATP control site.
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PMID:Reaction of cardiac myosin with a purine disulfide analog of adenosine triphosphate. I. Kinetics of inactivation and binding of adenylyl imidodiphosphate. 13 83

The Ca2+-activated myosin ATPase and the amino acid compositions of actin and myosin were determined for preparations from chronically failing dog hearts. Hypertrophy and congestive heart failure were produced by combined tricuspid valve insufficiency and pulmonary artery stenosis. Control, shamoperated, and noncardiac circulatory failure (inferior vena cava constriction) dogs also were studied. All hearts were divided into right ventricle, septum and left ventricle and each sample was individually analyzed. Calcium-activated ATPase decreased in the failing hearts and showed a distinct gradient of depression from right to left ventricles. There were no changes in ATPase activity among the other groups. The amino acid composition of actin was the same regardless of origin. The amino acid composition of myosin was unaltered except that cystine/2 residues were markedly decreased in failing heart myosin. The same gradient of depression was present as was found for Ca2+-activated myosin ATPase. This study suggests that protein metabolism is abnormal and that altered proteins are produced in hypertrophy and congestive heart failure. It appears that these changes do not affect all proteins, since actin was normal by the parameters studied. It is clear that the stressed ventricle is the most severely involved, but the entire heart is altered to some degree. Thus, we conclude that altered protein metabolism may be an important primary factor in the genesis of heart failure.
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PMID:The amino acid composition of actin and myosin and Ca2+-activated myosin adenosine triphosphatase in chronic canine congestive heart failure. 13 12

Histochemical fibre types classified in sections stained for succinic dehydrogenase (sdh) and myosin ATPase at pH 9.4, were found to be distributed in a consistent manner within the extensor digitorum longus (EDL) and 4 soleus muscles of the adult rat. Simple morphometric techniques applied to complete transverse sections of both muscles showed that the relative distributions and proportions of fibre types along their deep to superficial, and medial to lateral, axes varied accoording to the histochemical method used for fibre typing. Similar differences occurred when the relative ranges of size exhibited by each fibre type were compared in sections stained for SDH and ATPase, and the discrepancies in fibre classification were confirmed by an analysis of individual fibres in serial sections. The findings are discussed in relation to those previosly reported for the EDL and soleus muscles of the rat.
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PMID:The distribution and relative sized of fibre types in the extensor digitorum longus and soleus muscles of the adult rat. 14 Jan 60

N-(3-pyrene)maleimide adducts of myosin (PM-myosin) are fluorescent and possess actin-activated Mg2+ ATPase activity. Addition of ATP to PM-myosin produces a reversible decrease of 10% in fluorescence intensity of the pyrene fluorophore in the presence of actin. Analogues of ATP which are poor substrates for myosin ATPase or which merely dissociate actomyosin produce less decrease in fluorescence of PM-myosin than does ATP. Since fluorescence of acto-PM-myosin is sensitive to environmental changes associated with ATP hydrolysis, and/or with fluorophore-actin interactions. PM-myosin may be a useful analysis of molecular aspects of muscle contraction.
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PMID:Preparation and characterization of fluorescent N-(3-pyrene)maleimide adducts of myosin. 14 Feb 1


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