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)

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

Kinetic measurement of the reaction of dynein ATPase (ATP phosphohydrolase, EC 3.6.1.3) extracted from the gills of Mytilus edulis shows that in the presence of Mg2+ there is a very rapid initial liberation of Pi from the dynein-ATP system, followed by a slower liberation in the steady state. In view of following results, we have confirmed that this phenomenon is not due to the accumulation of end products, a fall in substrate concentration, nor to the presence of labile impurities in ATP but is due to the catalytic activity of dynein ATPase. 1. The replacement of native dynein by heat denatured dynein or other kinds of Mg2+-ATPase could not produce such a burst phenomenon under the same condition. 2. Both the rate of initial burst and that of steady state were proportional to enzyme content over a wide range under our standard condition. 3. Initial burst was also observed under the constant ATP level by using a ATP generate system. 4. Preincubation of dynein with Pi prior to initiation of the reaction did not eliminate the initial burst. Some properties of the initial rapid liberation of dynein ATPase were also examined. These are shown below. 5. The free ADP liberation did not show any initial burst though the Pi liberation did in the initial phase and the rate of free ADP liberation was almost equal to that of Pi liberation of the steady state. 6. Mg2+ was more effective than Ca2+ for the appearance of the initial burst while the liberation of Pi in the steady state was activated more by Ca2+ than by Mg2+. The addition of K+ in the presence of Mg2+ resulted in a marked increase of Pi liberation in the steady state but not in the initial state. 7. The activation energy of the initial burst was 9.7 kcal, which is slightly smaller than that of myosin ATPase.
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PMID:Studies on the initial phase of dynein ATPase activity. 13 33

Human cardiac myosin isolated from operatively obtained samples of ventricular septum and left ventricular free wall of subjects with asymmetric septal hypertrophy (ASH) was compared, with respect to structural and enzymatic properties, to myosin isolated from hearts of subjects without heart disease. The following parameters were studied: (1) activation of myosin ATPase activity by K+-EDTA and Ca2+, (2) molecular weight of the heavy and light chains of myosin as determined by electrophoretic migration in polyacrylamide-sodium dodecyl sulfate (SDS) gels and (3) ability to form bipolar aggregates at low ionic strength, as examined by electron microscopy. No difference was present in any of these parameters between human cardiac myosin from subjects with ASH and from subjects without heart disease. Thus, the genetic defect present in subjects with ASH is not expressed in the particular structural and functional characteristics of myosin evaluated in this study.
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PMID:Isolation and characterization of myosin from subjects with asymmetric septal hypertrophy. 14 25

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

Cardiac hypertrophy in the rabbit, secondary to pulmonary artery stenosis, results in a decrease in unloaded shortening velocity (Vmax) and maximum rate of isometric force development (dP/dtmax), while the peak isometric twitch tension is unchanged and time to peak tension (TPT) is increased. The principle hypothesis used to explain these results involve 1) slowing of myosin cross bridge movement as reflected in depressed myosin ATPase activity and 2) changes in excitation contraction coupling phenomena resulting in changes in intracellular Ca++ movement. Ca++ and actin activated myosin ATPase from the hypertrophied (H) muscles is depressed by 30%. Total initial heat, tension dependent heat and tension independent heat are depressed in H muscles by 57, 56, and 61% respectively. The rate of tension independent heat production in H preparations is depressed by 66%. From these data it is concluded that 61% of the depression in Vmax could be accounted for by the alteration in myosin with the reminder attributable to changes in EC coupling. Increased TPT can be accounted for by the change in rate of Ca++ flux as indicated by the alterated rate of tension independent heat evolution.
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PMID:The partitioning of altered mechanics in hypertrophied heart muscle between the sarcoplasmic reticulum and the contractile apparatus by means of myothermal measurements. 14 Jun 57

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+-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

The interaction of actin with myosin was studied in the presence of ATP at low ionic strength by means of measurements of the actin-activated ATPase activity of myosin and superprecipitation of actomyosin. At high ATP concentrations the ATPase activities of myosin, heavy meromyosin (HMM) and myosin subfragment 1 (S-1) were activated by actin in the same extent. At low ATP concentrations the myosin ATPase activity was activated about 30-fold by actin, whereas those of HMM and S-1 were stimulated only several-fold. This high actin activation of myosin ATPase was coupled with the occurrence of superprecipitation. The activation of HMM or S-1 ATPase by actin shows a simple hyperbolic dependence on actin concentration, but the myosin ATPase was maximally activated by actin at a 2:1 molar ratio of actin to myosin, and a further increase in the actin concentration had no effect on the activation. These results suggest the presence of a unit for actin-myosin interaction, composed of two actin monomers and one myosin molecule in the filaments.
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PMID:Presence of a unit for actin-myosin interaction during the superprecipitation of actomyosin. 14 84

A new, simple method for the isolation of actin from myxomycete plasmodia has been developed. Plasmodium myosin B was incubated at 55 degrees C for 15 min in the presence of ATP or was treated with 90% acetone. By this treatment myosin was denatured completely. Actin was then extracted with a dilute ATP and cysteine solution from the heat- or acetone-treated myosin B. The method is simple and almost pure actin was obtained in high yield. The purified G-actin polymerized to F-actin on addition of 0.1 M KCl or 2 mM MgCl2. The viscosity of the purified F-actin was 8-10 dl/g. The F-actin activated muscle myosin ATPase, and actomyosin synthesized from the F-actin and muscle myosin showed superprecipitation on addition of ATP.
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PMID:A simple method for the isolation of actin from myxomycete plasmodia. 14 66


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