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)

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

Mild pulmonic stenosis, induced in dogs by banding the pulmonary artery, elevated right ventricular peak systolic pressure to 60% above the control and elevated right ventricular K+- and Ca2+- activated myosin ATPase activities. In contrast, severe pulmonic stenosis, which elevated right ventricular peak systolic pressure to 300% above the control, did not produce an increase in myosin enzymatic ATPase Vmax values but caused a decrease in myosin activity. Mild aortic stenosis, induced by banding the ascending aorta, forcing a transaortic pressure gradient of 25 mm Hg, caused an elevation in left ventricular muosin ATPase, whereas severe aortic banding, brought about by creating a transaortic pressure gradient of 55 mm Hg, never caused an elevation in left ventricular myosin enzymatic Vmax values, but, like severe pulmonic banding, caused a decrease in K+- and Ca2+- activated myosin activities. Normal left ventricular myosin Vmax values in mumol of PO4/mg-min at 37 degrees C were: K+ = 2.84 +/- 0.22, and Ca2+ = 0.97 +/- 0.14. For right ventricular myosin they were: K+ = 2.15 +/- 0.16, and Ca2+ =0.74 +/- 0.10. Analyses of tissue gases, based on mass spectrometry data, showed that the hypertrophied ventricles had an elevated tissue pCO2 and an elevation in the cGMP/cAMP ratio.
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PMID:Differential responses of canine myosin ATPase activity and tissue gases in the pressure-overloaded ventricle dependent upon degree of obstruction: mild versus severe pulmonic and aortic stenosis. 20 99

Cardiac myosin from rats exercised 90 or 150 min daily for 8 wk was compared with the myosin from the hearts of matched sedentary controls. The Ca++-ATPase activity was increased 17 percent in rats exercised 90 min and 30 percent in rats exercised 150 min daily. In the exercised group 0.18 M KCl increased the myosin ATPase activity by 50 percent but had no effect in the control group. Ethylene glycol activated the Ca++-ATPase in control myosin preparations, but had no significant effect on myosin from conditioned hearts. Heavy meromyosin (HMM) from conditioned hearts had a higher Ca++-ATPase activity than from controls. Fluorescence with 8-anilinonaphthalene sulfonate (ANS) was increased 30 percent in HMM from conditioned hearts. The results suggest that the increased myosin ATPase activity in the hearts of exercised animals may be due to a local conformational change at or near the active site.
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PMID:Effects of physical training on cardiac myosin ATPase activity. 23 67

The conformations of the transitory intermediates of the myosin ATPase occurring during the hydrolytic cycle, enzyme without ligand, enzyme-substrate complex and two different forms of enzyme-product complex, have been characterized in terms of numbers and classes of reactive thiol groups based on incorporation of radioactively labeled alkylation reagent. The techniques employed allowed this to be done under steady-state conditions in the presence of high ligand concentrations on intact myosin from rabbit fast skeletal muscles at low ionic strength where the protein is in the gel state as it is in muscle. The binding of a divalent cation (Mg2+ or Ca2+) nucleotide complex exposes thiol-1 as well as thiol-2 groups. The long-lived ATPase intermediate occurring at temperatures above 10 degrees C adopts the same conformation with Mg2+ and Ca2+ ions. This intermediate does not protect the thiol-1 and thiol-2 groups but exposes a number of thiol-3 groups which seem to be located distant from the active site. The conformation of the intermediate prevailing in the presence of ATP changes with lowering temperature below 10 degrees C and is identical with that found in the presence of ADP at 0 degree C indicating a change in the rate-limiting step of the hydrolytic cycle. In the absence of divalent cations no such temperature-dependent change in conformation was observed. Evaluation of the activation entropies shows that the structure of the long-lived intermediate occurring above 10 degrees C in the presence of Mg2+ ions goes through a transformation from low to high order at around 20 degrees C. In the case of the monovalent-cation-stimulated ATPase a constant activation energy of around 70 kJ/mol, typical of many enzyme reactions, was found over the entire temperature range from 0--35 degrees C.
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PMID:Temperature-induced transitions in the conformation of intermediates in the hydrolytic cycle of myosin. 24 Jul 11

Muscle biopsy samples were obtained from healthy subjects in order to evaluate quantitative differences in single fibres of substrate (glycogen and triglyceride) and ion concentrations (Na+ and K+) as well as enzyme activity levels (succinate-dehydrogenase, SDH; phosphofructokinase, PFK; 3-hydroxyacyl-CoA-dehydrogenase, HAD; myosin ATPase) between human skeletal muscle fibre types. After freeze drying of the muscle specimen fragments of single fibres were dissected out and stained for myofibrillar-ATPase with preincubations at pH's of 10.3, 4.6, 4.35. Type I ("red") and II A,B, and C ("white") fibres could then be identified. Glycogen content was the same in different fibres, whereas triglyceride content was highest in Type I fibres (2-3 X Type II). No significant differences were observed for Na+ and K+ between fibre types. The activity for the enzymes studied were quite different in the fibre types (SDH and HAD, Type I is approximately 1.5 X Type II; PFK Type I is approximately 0.5 X Type II, Myosin ATPase Type I is approxiamtely 0.4 X Type II). The subgroups of Type II fibres were distinguished by differences in both SDH and PFK activities (SDH, Type II C is greater than A is greater than B; PFK, Type II B is greater than A is approximately C). It is concluded that contractile and metabolic characteristics of human skeletal fibres are very similar to many other species. One difference, however, appears to be than no Type II fibres have an oxidative potential higher than Type I fibres.
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PMID:Metabolic characteristics of fibre types in human skeletal muscle. 24 87

When studying enzymic and fluorescence properties of myosin and DTNB-treated myosin in the presence of K+, Na+, Li+, NH4+, Ca2+ and Mg2+ cations the following results were obtained. By the intrinsic protein fluorescence techniques no essential structural changes of myosin molecule at the dissociation of the DTNB light chain and activation myosin ATPase in the presence of different cations were found. The decrease of K+-EDTA-, the increase of Mg2+-activated and the stability of Ca2+-activated myosin ATPase may be the result of the modification of SH1 or SH2 sulfhydryl groups when treating the DTNB myosin in our conditions. The different level of decrease of the K+- and NH4+-activated myosin. ATPase may be explained by the fact, that myosin sulfhydryl groups have different effects on the activation of its ATPase by these cations.
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PMID:[Comparative study of myosin and DTNB-treated myosin with regard to ATP activity and fluorescence]. 97 74

The heart is not spared from the catabolic effects of undernutrition, but is subject to the same degree of weight loss as skeletal muscle. Pumping performance, however, is not reduced in proportion to myocardial wasting and thus functional protection prevents failure of the hypotrophic heart. In animal experiments, no major qualitative changes in myocardial composition apart from reduced myosin ATPase activity have been found. This reduction in ATPase activity might be associated with down-regulation of thyroid hormones and the development of insulin resistance and serve as an energy saving adaptation. Increased cardiac sensitivity to adrenergic stimulation may also constitute a means to increase heart performance in situations with augmented circulatory demands. On the other hand, increased sensitivity and maximum response to adrenergic stimulation might render the heart more susceptible to arrhythmia, and thus explain sudden unexpected death following rapid weight loss.
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PMID:Cardiac effects of caloric restriction-mechanisms and potential hazards. 132 44

1. Experiments were carried out to examine the biochemical changes, such as contractile protein biochemistry and membrane bound enzyme alterations associated with skeletal muscles of myd/myd. 2. Our studies demonstrate that there was a progressive decline in myofibrillar ATPase activity, and this decrease is greatest in 30 weeks old animals of myd/myd as compared to controls. 3. The proteolytic activity of myofibrils isolated from myd/myd was significantly higher than controls. 4. There was no significant difference in Ca2+ ATPase activity of myosin and actin-activated myosin ATPase activity of myd/myd and their controls. 5. Mg2+ ATPase and Na(+)+K(+)-ATPase of myodystrophic SL showed significant increase compared to controls. 6. Isoproterenol stimulated adenylate cyclase activity was significantly lower in the SL of dystrophic mice compared to controls. 7. GTP+isoproterenol stimulate adenylate cyclase was significantly higher in control SL and SR when compared to SL and SR isolated from myd/myd. 8. Guanylate cyclase activity was greater in myodystrophic mice both in the absence and presence of Triton X-100. cGMP and cAMP phosphodiesterase activities were greater in dystrophic mice as compared to controls. 9. These observations suggest that there are significant changes in myofibrillar ATPase, myofibrillar protease and membrane bound enzymes of myd/myd compared to control.
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PMID:Myofibrillar and membrane-bound enzymes in skeletal muscle from myodystrophic mice. 135 51

Caldesmon is an actin-binding protein present in smooth muscle cells that also inhibits actin-activated myosin ATPase activity. To assess the possible role of caldesmon in the regulation of smooth contraction, we investigated the effects of synthetic peptides on force directly recorded from single hyperpermeable smooth muscle cells of ferret aorta and portal vein. GS17C, a peptide that contains the residues from Gly651 to Ser667 of the caldesmon sequence plus an added cysteine at the C terminus, binds calmodulin in a Ca(2+)-dependent manner and also binds to F-actin but does not inhibit actomyosin ATPase activity (Zhan, Q., Wong, S.S., and Wang, C.-L.A. (1991) J. Biol. Chem. 266, 21810-21814). In cells in which Ca2+ was clamped at pCa 7.0, GS17C induced a dose-dependent contraction (EC50 = 0.92 microM) in aorta cells, whereas it evoked little or no contraction in portal vein cells. The GS17C-induced contraction in aorta cells was inhibited at higher Ca2+ concentrations (above pCa 6.6) and by pretreatment with calmodulin. Another peptide, C16AA, which contains the residues from Ala594 to Ala609 and does not bind actin or calmodulin, did not induce contraction. Our results strongly suggest that GS17C induces contraction by the displacement of the inhibitory region of endogenous caldesmon and, furthermore, that caldesmon present in these smooth muscle cells regulates contraction by providing a basal resting inhibition of vascular tone.
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PMID:Regulation of vascular smooth muscle tone by caldesmon. 138 78


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