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)

The mechanisms by which the aged heart adapts to a superimposed pressure load such as hypertension have not been described. We therefore investigated biochemical and molecular genetic adaptations in the 24-month-old rat heart subjected to renovascular hypertension. Compared with 4-month-old rats, aging was associated with a 68% increase in left ventricular mass without any change in heart weight-to-body weight ratio, a 33% reduction in calcium-activated myosin ATPase activity, and a shift from a V1 to a V3 predominant myosin heavy chain (MHC) isoform distribution. A 46% reduction in alpha-MHC mRNA and a reciprocal increase in beta-MHC mRNA was seen. When hypertension was superimposed, there was a further 75% increase in ventricular mass, a 63% increase in heart weight-to-body weight ratio, and a 19% reduction in myosin ATPase. Myosin isozyme distribution was further shifted to V3, and the ratio of alpha-MHC to beta-MHC mRNA was reduced. In addition, with hypertension a significant (greater than 50%) reduction in the mRNA level of the cardiac sarcoplasmic reticular calcium-activated ATPase was seen. These data demonstrate that the aged myocardium is able to respond to a superimposed pressure load with a molecular genetic and protein synthetic pattern of hypertrophy analogous to that seen in younger animals.
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PMID:Effect of aging and hypertension on myosin biochemistry and gene expression in the rat heart. 183 8

The amino-terminal region of actin participates in the binding of myosin subfragment 1 (S1) during cross-bridge cycling, thereby assisting in the activation of the magnesium-dependent myosin ATPase. Effects of three actin fragments on the magnesium-dependent S1 and acto-S1 ATPase activities in solution were studied. One of the peptides, containing residues actin 1-44, mimicked the S1 ATPase-activating properties of actin and in turn inhibited acto-S1 ATPase both in a concentration-dependent manner. This suggests peptide competition for the actin binding site on myosin. The other fragments, residues actin 1-18 and 82-119, respectively, had no detectable effect on S1- and acto-S1 ATPase activity.
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PMID:Peptide competition of actin activation of myosin-subfragment 1 ATPase by an amino terminal actin fragment. 183 34

Different histochemical identification methods for muscle fibre types have been introduced over the years. Most of them have been based on myosin ATPase activity after different kinds of preincubations, alone or in combination with oxidative enzymes. Comparative studies have shown, however, that the different methods result in nonidentical subgroups of type II fibres. Optical density values of individual fibres after incubation of serial sections for alkali- or copper-preincubated ATPase, NADH-TR, and fibre diameter, combined in two-dimensional plots, have for a long time been used in our laboratory to separate three subgroups of type II fibres. A cluster analysis, based on the data mentioned above, results in three subgroups of type II fibres in rat plantaris muscle. In comparison, earlier studies comparing different histochemical methods and reporting lack of correspondence between them have been based on two subgroups of type II fibres only. It is suggested that part of the lack of correspondence is due to unequal and incomplete separation by the methods used in the comparative studies, and that the three subgroups of type II fibres identified in the cluster analysis are type IIA, IIX and IIB, respectively. The need for a consensus on a common basis for histochemical identification of muscle fibre types is emphasized.
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PMID:How unequivocal is the muscle fibre type concept? 183 5

Chicken gizzard actomyosin, containing the calmodulin-myosin light chain kinase (MLCK) system, was incubated in the presence of various concentrations of PSK, a protein-bound polysaccharide from Basidiomycetes, together with Ca2+ and Mg-ATP. The phosphorylation of myosin was enhanced half-maximally by 10-4 g/ml of PSK. However, a similar concentration of PSK reduced the Mg-ATPase activity of the actomyosin. The former was brought about through stimulation of the MLCK activity and the latter through inhibition of the myosin ATPase activity.
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PMID:A protein-bound polysaccharide from Basidiomycetes enhances myosin phosphorylation but inhibits myosin ATPase activity: studies with a crude actomyosin preparation of chicken gizzard smooth muscle. 183 24

The effects of C-protein on actin-activated myosin ATPase depending on Ca(2+)-level and LC2-phosphorylation were studied. Column-purified myosin and non-regulated actin were used. At ionic strength of 0.06 C-protein inhibits actomyosin ATPase activity both in the presence and in the absence of calcium, more effective in the case of dephosphorylated myosin. For this myosin, at mu = 0.12 C-protein activates actomyosin ATPase at pCa4, but slightly inhibits at pCa8. No such effects have been observed in the case of phosphorylated myosin. The possibility of coordinative action of LC2-chains and C-protein in regulatory mechanism of skeletal muscle contraction is discussed.
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PMID:Ca(2+)-dependent effects of C-protein on the actin-activated ATPase of phosphorylated and dephosphorylated skeletal muscle myosin. 183 95

Permeabilized endothelial cell monolayers retracted on exposure to ATP and Ca2+. ADP, inosine triphosphate (ITP), GTP, adenosine 5'-(gamma-thio)triphosphate (ATP-gamma S), and 5'-adenylylimidodiphosphate failed to support retraction. However, ATP gamma S, a substrate for myosin light-chain kinase (MLCK) but not myosin adenosinetriphosphatase (ATPase), combined with ITP, a substrate for myosin ATPase but not MLCK, supported retraction. Two MLCK pseudosubstrate peptides, M5 and SM-1, inhibited endothelial cell retraction equally and more effectively than myosin kinase-inhibitory peptide with a sequence based on the phosphorylated site of myosin light chain. M5 was shown to inhibit thiophosphorylation of endothelial cell myosin light chains. Endothelial cells incubated with exogenous unregulated kinase in the presence of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra-acetic acid retracted on addition of ATP. This retraction was accompanied by thiophosphorylation of the 19 kDa myosin light chains in the presence of ATP gamma 35S. The N-ethylmaleimide-modified subfragment 1 of myosin heads, a specific inhibitor of actin-myosin interaction, prevented retraction. These data add support to the proposal of a central role for MLCK activation of myosin in endothelial retraction.
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PMID:Regulation of permeabilized endothelial cell retraction by myosin phosphorylation. 185 58

After myocardial infarction in rats, muscle performance in the remaining hypertrophied myocardium deteriorates and is associated with a decrease in myosin adenosinetriphosphatase (ATPase) activity and a shift to the V3 myosin heavy-chain isoform. We have previously shown in another model of hypertrophy, secondary to renovascular hypertension, that chronic intermittent adrenergic stimulation with dobutamine (Db) can prevent this biochemical adaptation. The present study was undertaken to assess the effects of chronic Db treatment on cardiac mass, function, metabolism, and myosin biochemistry in animals subjected to chronic myocardial infarction. Four groups of rats were studied: controls, animals treated with Db (2 mg/kg 2X daily for 4 wk), animals subjected to myocardial infarction and killed after 4 wk (MI), and MI animals concurrently treated with Db for 4 wk (MI-Db). The two MI groups were subdivided into those with and without congestive heart failure (CHF). Heart weight was increased by 13% with Db, unchanged in the infarct groups without CHF, and increased by 9 and 22% in the infarct groups with CHF. Db did not have any additional effect on heart weight in these later groups. Infarct weight was greatest in the animals with CHF, and viable myocardium was equivalent in all infarct groups suggesting that CHF was associated with a greater degree of hypertrophy. Ventricular performance, as assessed in an isovolumic heart apparatus, was markedly depressed in both infarct groups with CHF and was not affected by Db. Db increased myosin ATPase activity in control and infarcted animals both with and without congestive heart failure. Myosin oxygen consumption and lactate production were not adversely affected by Db.
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PMID:Effects of chronic dobutamine on cardiac mechanics and biochemistry after myocardial infarction in rats. 199 90

Left ventricular papillary muscle function, transmembrane action potentials, myosin adenosinetriphosphatase (ATPase) and isoenzyme distribution, and myocardial pathology were studied in hypertensive (H), diabetic (D), hypertensive-diabetic (HD), and control (C) rats. There was approximately 50% relative left ventricular hypertrophy in H and HD rats. Relative lung and liver weights were greater in HD rats. Peak velocity of shortening tended to decrease progressively in H, D, and HD rats. The duration of contraction and relaxation was markedly prolonged in Ds and HDs. The length-developed tension relation was blunted in HDs. The negative inotropic effect of verapamil was similar in all groups. Resting membrane potential and amplitude were decreased in D and HD rats. Action potential duration was increased in H, D, and especially HD rats. The shortening of action potential duration with increased stimulus frequency was greater in H, D, and especially HD rats than in Cs. Left ventricular myosin ATPase and V1 isoenzyme content decreased progressively in H, D, and HD rats. Right ventricular V1 isoenzyme content was not affected in H rats but was markedly decreased in D and HD rats. Left (and right) ventricular pathology was unchanged in rats with diabetes but was increased in rats with hypertension. These data suggest that the combination of myocardial pathology (due to hypertension) and cellular dysfunction (caused mainly by diabetes) may result in cardiomyopathy and congestive heart failure in the HD rat.
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PMID:Hypertensive-diabetic cardiomyopathy in rats. 213 24

1. Two types of myosins with phosphorylated and dephosphorylated myosin light chains were prepared from Drosophila flies. The former had ATPase (Ca2(+)- and Mg2(+)-activited) activities twice those of the latter. 2. The myosin phosphorylated with crude myosin light chain kinase from flies showed ATPase (Ca2(+)- and Mg2(+)-activated) activaties twice those of the dephosphorylated myosin. 3. It is suggested that phosphorylation of myosin light chains several hours after emergence stimulates myosin ATPase activity so as to facilitate the flight function of the fruitfly.
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PMID:Regulation of Drosophila myosin ATPase activity by phosphorylation of myosin light chains--I. Wild-type fly. 213 97

Cardiac myofibrils from cardiomyopathic hamsters exhibit elevated Mg2+ ATPase activity and a parallel upward shift of the calcium ATPase dose response curve. To explore the mechanism, myofibrils from control and cardiomyopathic hamster hearts were incubated with isolated troponin-tropomyosin complex (Tn.Tm) from cardiomyopathic and control hamster or from dog hearts. Tn.Tm from control hamster or dog hearts restored normal Mg2+ ATPase activities to myofibrils from myopathic hearts. However, the maximum ATPase response to calcium stimulation was less in cardiomyopathic myofibrils compared to controls, even when control Tn.Tm was included. Electrophoretic patterns of Tn.Tm from myopathic and control hearts were similar. Electrophoresis of the hamster myofibrils mixed with dog cardiac Tn.Tm and then washed demonstrated binding of this complex to myopathic myofibrils. To further confirm that the incubation experiments resulted in binding, 125I troponin-tropomyosin was cross-hybridized with myofibrils, extensively washed, and then analyzed enzymatically and autoradiographically. Autoradiograms demonstrated similar percent binding of 125I Tn.Tm to all myofibrillar preparations and enzymatic effects like those found using cold Tn.Tm. These studies suggest that Tn.Tm from cardiomyopathic hearts inhibits Mg2+ myofibrillar ATPase activity to a lesser degree than Tn.Tm from control hearts. Decreased stimulation by calcium in myopathic preparations may be due to abnormalities in troponin-tropomyosin and/or to the decreased myosin ATPase activity observed previously.
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PMID:Troponin-tropomyosin abnormalities in hamster cardiomyopathy. 214 67


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