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)

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

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

Single muscle fibres were isolated by microdissection from freeze-dried samples of rabbit psoas and soleus muscles. The individual fibres were typed according to qualitative histochemical reactions for succinate dehydrogenase or NADH-tetrazolium reductase and for alkaline Ca2+-activated myofibrilla myosin ATPase after acid or alkaline preincubation. Methods are described for electrophoretic analysis by means of polyacrylamide disc electrophoresis in the presence of SDS of total myofibrilla proteins in single fibres after pre-extraction of soluble proteins. Fast-twitch white fibres revealed a myosin light chain pattern characteristic of "fast- type" myosin with three light chains of apparent molecular weights of 22,300 (LC1) 18,400 (LC2) and 16,000 (LC3). Fast-twitch red fibres were indistinguishable in this respect from fast-twist white fibres and showed an identical pattern of myosin light chains. Slow-twitch fibres could be characterized by a myosin light chain pattern typical of myosin of slow-twitch muscles with peptides of the apparent molecular weights of 23,500 (LC1Sa), 23,000 (LC1Sb) and 18,500 (LS2S). Slow-twitch fibres isolated from soleus as well as from psoas muscle were indistinguishable with regard to their myosin light chain patterns, thus suggesting that fibres of the same histochemical type correspond in their myosin light chain patterns irrespective of their origin from different muscles.
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PMID:Myosin light chain patterns of individual fast and slow-twitch fibres of rabbit muscles. 14 18

The moles of calcium bound by the left ventricle were 1.5 +/- 0.1, while those of the right ventricle were 2.9 +/- 0.2. The calcium binding constants were the same between myosins of the two cardiac ventricles. The Ca2+ binding constants were approximately 1.1 X 10(5) M-1 for both left and right ventricular myosins. Left ventricular myosin bound 1.3 +/- 0.1 mol of Mn2+, whereas right ventricular myosin bound 2.8 +/- 0.1 mol of Mn2+. The divalent cation Mn2+ only partially competed out Ca2+ (50%). Because of the partial competition, it seemed that Ca2+ and Mn2+ had some sights in common. These studies demonstrate a twofold difference in divalent cation binding (Ca2+, Mn2+) between left and right ventricular myosins. This variation in cation binding between the two ventricles is reflected in similar differences in myosin ATPase activity between the two ventricles.
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PMID:Binding of divalent cations by canine cardiac myosin: differences in normal right and left ventricles dependent upon number of light chains. 14 25

Human cardiac myosin isolated from operatively obtained samples of ventricular septum and left ventricular free wall of patients with asymmetric septal hypertrophy (ASH) was compared, with respect to structural and enzymatic properties, to myosin isolated from hearts of patients 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 SDS-polyacrylamide 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 patients with ASH and from patients without heart disease. Thus, the genetic defect present in patients with ASH is not expressed in the particular structural and functional characteristics of myosin evaluated in this study.
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PMID:Characterization of myosin from patients with asymmetric septal hypertrophy. 14 40

Preparations of ATP from equine muscle contained an inhibitor of dynein Mg2+-activated ATPase. The inhibitory material was separated from the ATP by molecular sieve filtration. The several molecular species of dynein extracted from three different axonemal sources were all inhibited; myosin ATPase was not. With increasing amounts of inhibitor the inhibition did not go to completion but reached a plateau when the rate had been reduced to 1/5 the uninhibited rate. A plot of 1/[S] against 1/v at several inhibitor concentrations yielded parallel lines. There was little inhibition of dynein ATPase when Mg2+ was replaced by Ca2+. The inhibitor appeared slightly smaller in molecular size than ATP, had anionic character, and was not adsorbed to charcoal.
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PMID:A dynein ATPase inhibitor isolated from a commercial ATP preparation. 14 8

Changes in cardiac metabolism in myocardial failure and after alcohol ingestion are discussed. The main effect of alcohol ingestion is loss of cardiac contractility. Since heart muscle does not contain alcohol dehydrogenase, its toxicity is probably the result of a direct toxic effect of ethanol and acetaldehyde on the myocardial cell, possibly involving various membrane systems. Alcohol inhibits mitochondrial respiration and the activity of enzymes in the tricarboxylic acid cycle, and its interferes with both mitochondrial calcium uptake and binding. Ethanol profoundly affects myocardial lipid metabolism. Acetaldehyde diminishes myocardial protein synthesis and inhibits Ca++-activated myofibrillar ATPase. In myocardial failure, a series of possibilities may be responsible for the loss of contractility. Excitation-contraction coupling could be disturbed at the level of the sarcolemma, at the sarcoplasmic reticulum, at the mitochondria, and between calcium and the regulatory proteins. Deficiencies in Ca++ delivery systems of excitation-contraction coupling on the myosin ATPase activity could be responsible for the dimunition in cardiac contractility. Mitochondrial function may also be involved, since mitochondria from failing human hearts are defective with respect to respiratory control and calcium accumulation. Under certain conditions, the relationship of mitochondria to calcium sequestration is very important in influencing contractility. The involvement of contractile and regulatory proteins in myocardial failure cannot be excluded.
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PMID:Cardiac metabolsim: its contributions to alcoholic heart disease and myocardial failure. 15 68

Myosin light chain kinases have been isolated from rat thigh and rabbit skeletal muscle and cultured rat myoblasts. From these preparations, two types of kinases can be distinguished: calcium-dependent and calcium-independent. Both types of kinases can phosphorylate isolated P-light chains of myosin from several sources (skeletal muscle, cardiac muscle, and platelet). Data are shown which support the phosphorylation of the same site on the non-muscle P-light chains by both types of kinases. The rates of these reactins are, however, different for the two types of kinases. Kinetic analysis of the myoblast kinase shows differing affinities for various P-light chains (non-muscle greater than cardiac greater than skeletal). In the proliferative rat myoblast, phosphorylation of myosin is a prerequisite for actin activation of the myosin ATPase activity.
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PMID:A comparative study of the myosin light chain kinases from myoblast and muscle sources. Studies on the kinases from proliferative rat myoblasts in culture, rat thigh muscle, and rabbit skeletal muscle. 15 62


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