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)

Myosin was purified from rabbit alveolar macrophages in a form that could not be activated by actin. This myosin could be phosphorylated by an endogenous myosin light chain kinase, up to 2 mol of phosphate being incorporated/mol of myosin. The site phosphorylated was located on the 20,000-dalton myosin light chain. Phosphorylation of macrophage myosin was found to be necessary for actin activation of myosin ATPase activity. Moreover, the actin-activated ATPase activity was found to vary directly with the extent of myosin phosphorylation, maximal phosphorylation (2 mol of Pi/mol of myosin) resulting in an actin-activated MgATPase activity of approximately 200 nmol of Pi/mg of myosin/min at 37 degrees C. These results establish that phosphyoyration of the 20,000-dalton light chain of myosin is sufficient to regulate the actin-activated ATPase activity of macrophage myosin.
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PMID:Macrophage myosin. Regulation of actin-activated ATPase, activity by phosphorylation of the 20,000-dalton light chain. 15 17

Myosins purified from cardiac (porcine heart) and smooth (chicken gizzard) muscles were modified with 2,4,6-trinitrobenzenesulfonate (TNBS) and the effects on the kinetic properties of myosin ATPase [EC 3.6.1.3] were studied. The following results were obtained. 1. About 0.5 mol of TNBS per mol of myosin head was incorporated rapidly, irrespective of the presence of PP1 (2mM), into both types of myosin studied. 2. The size of the initial burst of P1 liberation for both myosins was found to be 0.5--0.6 mol/mol head. 3. The rapid incorporation of TNBS into cardiac muscle myosin was accompanied by a rapid decrease in the size of the initial P1 burst, and it was completely lost after modification for 20 min. However, smooth muscle myosin retained its P1 burst. 4. The EDTA (K+)-ATPase activity of both myosins modified in the presence or absence of PP1 decreased sharply with incorporation of TNBS. 5. Superprecipitation and ATPase activity of reconstituted actomyosin from cardiac myosin and skeletal F-actin decreased only after 10 min of modification with TNBS in the absence of PP1. 6. The spectra of TNP bound to myosins from cardiac and smooth muscles were unchanged by the addition of PP1. The above findings are compared with those previously obtained for skeletal muscle myosin [Miyanishi, T., Inoue, A., & Tonomura, Y. (1979) J. Biochem. 85, 747--753], and the structural and functional differences among the myosins derived from skeletal, cardiac, and smooth muscles are discussed.
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PMID:Modification of cardiac and smooth muscle myosins with 2,4,6-trinitrobenzenesulfonate. Evidence for differences in structure around the active sites of cardiac, smooth, and skeletal muscle myosin ATPase. 15 5

A plasma-membrane fraction was isolated from a post-nuclear extract of human neutrophils by centrifugation through a linear sucrose density gradient. This fraction exhibited a Ca2+-dependent adenosine triphosphatase (ATPase) activity that could be differentiated from mitochondrial or myosin ATPase and from plasma-membrane Mg2+-dependent ATPase. When assayed in the presence of [gamma-32P]ATP, the Ca2+-dependent ATPase reaction resulted in the formation of an acid-resistant hydroxylamine-sensitive bond between the gamma-[32P] phosphate group and a membrane protein subunit with an apparent mol.wt. of 135000. Half-maximal activating effect of Ca2+ was found at 82nM and 0.18 microM for the ATPase and the formation of the 32P-membrane complex respectively. Generation of the phosphorylated product attained the steady state at 0 degrees C by about 30s, and was rapidly reversed by ADP. These results suggest that the Ca2+-activated ATPase reaction occurs through the formation of a phosphoprotein intermediate, similar to that described for some Ca2+-dependent ATPase enzymes associated with Ca2+ transport. The possibility thus exists that the neutrophil Ca2+-dependent ATPase catalyses a process of Ca2+ extrusion from the cell, thereby participating in the regulation of several Ca2+-dependent neutrophil functions.
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PMID:Calcium ion-dependent adenosine triphosphatase activity and plasma-membrane phosphorylation in the human neutrophil. 16 Feb 22

1. Using histochemical staining methods for myosin ATPase oxidative and glycolytic enzymes, three major types of muscle fibre could be identified in the skeletal muscle of hamsters and mice. 2. Muscle fibre counts showed that the proportions of the different fibres were not entirely stable with age. In the hamster biceps brachii which is predominantly composed of ATPase-high fibres there was a decrease in the number of ATPase-low fibres. In the soleus muscle which is predominantly composed of ATPase-low fibres there was a decrease in ATPase-high fibres with age. 3. Although there was a change in the proportions of fibre types there was no change in the total number of fibres within the muscles with age. It is suggested that some reinnervation may take place during growth and that this is why the less dedominant fibre type decreases. 4. The response of the different fibre types to partial starvation was studied. The ATPase-high fibres showed the greatest decrease in size. Of these, the ATPase-high glycolytic type responded more than the ATPase-high oxidative type. The effects of the under-nutrition on the different fibre types were found to be completely reversible. Starvation did not affect the total number of fibres or the numbers of any fibre type. 5. The response of the different types to high intensity exercise (weight lifting) was studied. This type of exercise resulted in hypertrophy of all three major fibre types. However, the extent of the response varied according to the fibre type and the exact nature of the exercise. In most cases the ATPase-high fibres underwent hypertrophy more readily than the ATPase-low fibres. Where distinction was made between the two types of ATPase-high fibres, the ATPase-high glycolytic were found to hypertrophy more than the ATPase-high oxidative fibres. The effects of post exercise recovery (return to relative inactivity) were also studied and the changes in size of the fibres were found to be completely reversible.
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PMID:Changes in rodent muscle fibre types during post-natal growth, undernutrition and exercise. 16 Sep 29

Whereas dissociation of rabbit skeletal muscle myosin light chains occurs at an increased temperature (25 degrees) and in the absence of divalent cations, reassociation of the myosin oligomer requires a low temperature (4 degrees C) and the presence of divalent cations, thus resulting in the original light to heavy chain stoichiometry. With a 5-10 per cent release of alkali light chains, LC1 and LC3, and a 50 per cent dissociation of the Ca2+ binding light chain, LC2, there is no significant decrease in myosin ATPase activity irrespective of the cation activator, however, there is an approximate 15-20 per cent decrease in actomyosin ATPase activity. With reassociation of the myosin oligomer, actomyosin ATPase activity is partially restored as well as the original number of Ca2+ binding sites.
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PMID:Dissociation and reassociation of rabbit skeletal muscle myosin. 16 9

Myosin isolated under phosphorylation conditions, showed an additional band of phosphorylated light chain. In the case of cardiac myosin, LC2 is the phosphorylated light chain whereas in skeletal myosin, it is the 18,000 dalton component known as DTNB light chain. There are no differences in K+-EDTA and Ca2+ activated myosin ATPase of cardiac and skeletal of control and phosphorylated myosins. Our experiments showed that the rat heart and skeletal muscle myosins isolated under phosphorylating conditions exhibited high phosphate content which is associated with higher actin activated Mg2+ ATPase activity of myosin as compared to control. Control myosin phosphorylated using myosin light chain kinase and Ca2+ also showed high actin activated myosin ATPase activity. Beef heart myosin isolated in the presence of phosphate buffer, also exhibited a higher level of phosphate followed by an increase in actin activation as compared to myosin isolated in the absence of phosphate buffer. All these experimental data suggest that there is a direct relationship between actin activation and the amount of phosphate incorporated as a result of phosphorylation.
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PMID:Phosphorylation and its effects on ATPase activity of cardiac and skeletal myosins. 16 48

The kinetic parameters of the inhibition of monovalent cation activated myosin ATPase by ADP were investigated. The inhibitor constant (KI) was 1.65 X 10(-4) M and the maximal velocity (V) was 1.28 mumol Pi/mg myosin/min in the presence of 0.3M Kcl at 20 degrees C. The dependence of 1/VO on inhibitor concentration and the pH dependence of KI and Km (i.e. pKi approximately equal to pKm) show that the inhibition has a pure competitive character. The results are supported by energetic parameters, too. The enthalpy of the formation of (EI) complex was calculated. Similar results were obtained also in the presence of Rb+ activated myosin ATPase and subfragment-I K+ ATPase.
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PMID:Kinetic study of the inhibition of myosin ATPase activity by ADP. 16 61

Electron-microscopic, morphometric, histochemical and biochemical studies were carried out on muscle biopsies from a patient with the characteristic clinical and pathological findings of nemaline myopathy. The mean fiber diameter was decreased, and the vastus lateralis muscle biopsy consisted exclusively of slow twitch (Type I) fibers. Quantitative biochemical investigations revealed significantly low calcium uptake and ATPase activity of the fragmented sarcoplasmic reticulum and decreased myosin ATPase activity. The electrophoretogram of myosin showed an abnormality in the light chain pattern which could not be explained by a disproportion of normal fiber types.
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PMID:Characteristics of myosin in nemaline myopathy. 17 35

A 35--70% ammonium sulfate fraction of smooth muscle actomyosin was prepared from guinea pig vas deferens. This fraction also contains a smooth muscle myosin kinase and a phosphatase that phosphorylates and dephosphorylates, respectively, the 20,000-dalton light chain of smooth muscle myosin. Phosphorylated and dephosphorylated smooth muscle myosin. Phosphorylated and dephosphorylated smooth muscle myosin were purified from this ammonium sulfate fraction by gel filtration, which also separated the kinase and the phosphatase from the myosin. Purified phosphorylated and dephosphorylated myosin have identical stained patterns after sodium dodecyl sulfate/polyacrylamide gel electrophoresis. They also have similar ATPase activities measured in 0.5 M KCl in the presence of K+-EDTA and Ca2+. However, the actin-activated myosin ATPase activity is markedly increased after phosphorylation. Moreover, the actin-activated ATPase activity of phosphorylated myosin is inhibited by the removal of Ca2+ in the absence of any added regulatory proteins. Dephosphorylation of myosin results in a decrease in the actin-activated ATPase activity. Skeletal muscle tropomyosin markedly increased the actin-activated ATPase activity of phosphorylated but not dephosphorylated myosin in the presence, but not in the absence, of Ca2+.
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PMID:Effect of phosphorylation of smooth muscle myosin on actin activation and Ca2+ regulation. 18 2

A quantitative study of the tibialis anterior muscle of the adult rat showed that the proportions of each 'histochemical' fibre type varied between adjacent regions along the deep to superficial and medial to lateral axes of the muscle. The distribution of fibre types classified with oxidative enzymes was similar to that using phosphorylase, but differed from that obtained with sections stained for myosin ATPase. This apparent discrepancy in classifation was confirmed by comparison of the ranges of fibre cross sectional areas for each fibre type classified on the basis of their oxidative enzme and ATPase activites, and by an independent analysis of individual fibres in serial sections stained for succinic dehydrogenase and ATPase.
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PMID:The distribution and relative sizes of three histochemical fibre types in the rat tibialis anterior muscle. 19 Jan 98


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