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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The procedure for the isolation of the highly active fraction of sarcoplasmic reticulum from pigeon and dog hearts is described. The method is based on the partial loading of heart microsomes with calcium and oxalate ions and the precipitation of loaded vesicles in sucrose and potassium chloride concentration gradients. Preparations obtained possess high activity of Ca2+-dependent ATPase and are also able to accumulate up to 10 mumol Ca2+ per mg protein. Purification of sarcoplasmic reticulum membranes is accompanied by a decrease in concentration of cytochrome a+a3 and an increase in the content of [32P]phosphoenzyme. The basic components in "calcium-oxalate preparation" from hearts are proteins with molecular weights of about 100000 (Ca2+-dependent ATPase) and 55000 Calcium-oxalate preparation from pigeon hearts was used for subsequent purification of Ca2+-dependent ATPase. Specific activity of purified enzyme from pigeon hearts is 12-16 mumol Pi/min per mg protein. Enzyme activity of purified Ca2+-dependent ATPase is inhibited by EGTA and is not sensitive to azide, 2,4-dinitrophenol and ouabain. The data obtained demonstrate the similarity of calcium pump systems and Ca2+-dependent ATPases isolated from heart and skeletal muscles.
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PMID:Isolation of calcium pump system and purification of calcium ion-dependent ATPase from heart muscle. 0 44

Like all inhalation anesthetics, halothane (CF3CHBrCl) has a dose-dependent negative inotropic effect on cardiac muscle. The mechanism of the action has not been determined, although effects on glycolysis, mitochondrial respiration and calcium kinetics, and sarcoplasmic reticulum ATPase activity have been suggested. Previous studies of the effect of halothane on the ATPase of contractile protein suffered from design and dosing defects. We have measured ATP splitting by canine cardiac natural actomyosin using extraction and equilibration procedures described previously (Honig, C. R. and Reddy, Y. C. 1973, J. Pharmacol. 184: 330-338). Drug dosing calculations were facilitated by measurement of the partition coefficient of halothane in protein. Halothane shifted the Ca++ concentration effect curve for actomyosin ATPase activity to the right. The maximum depression occurred at pCa 7.0 or 6.5. The effect was dose dependent with less than 10 percent depression at threshold and 50-60 percent depression at peak. Enzyme inhibition was antagonized by high Ca++ concentration, and was reversed by removing halothane from the reaction mixture. We suggest that inhibition of ATP utilization by the contractile system may be a mechanism of the in vivo myocardial depression produced by halothane.
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PMID:Halothane decreases actomyosin ATPase activity: a possible mechanism of the negative inotropic effect. 12 60

The stimulation by calcium and magnesium of ATPase activity of isolated ghosts, of water-soluble protein (spectrin), and of residual vesicles, derived from normal erythrocytes and from hereditary spherocytes (H.S.), has been measured. The ATPase activity found in normal water-soluble protein (WSP) at low levels of calcium (0.1-2.0 mM) is essentially absent in H.S. water-soluble protein, but the ATPase activity with magnesium and with high levels of calcium (60-100 mM) is the same in H.S. and normal WSP. Compared to normal, H.S. ghosts have increased Mg2+-stimulated activity. This increased activity is retained by the sedimentable vesicles ("residue") after extraction of the ghosts with 0.025 mM EDTA. The Ca2+, Mg2+-ATPase associated with the calcium pump is not significantly different in H.S.
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PMID:Absence of one component of spectrin adenosine triphosphatase in hereditary spherocytosis. 12 93

Using a rapid method of preparation, spectrin has been isolated from human erythrocytes and its ATPase activity investigated. The ATPase activity with calcium has two distinct components, one with optimal activity when calcium and ATP are of equal concentration (low-Ca-ATPase) and another which is activated above 1 mM CaCl2 and is maximal at 100 mM CaCl2. There is also a Mg-ATPase with maximal activity at 10 mM MgCl2. The high-Ca-ATPase of spectrin, but not the low-Ca-ATPase, is inhibited by magnesium, while the Mg-ATPase is inhibited by Ca in excess of ATP. None of these activities exhibits the calcium-stimulated magnesium-dependent activity characteristic of the red cell calcium pump.
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PMID:Calcium and magnesium ATPases of the spectrin fraction of human erythrocytes. 12 59

Temporal patterns of biosynthesis of the Ca2+ + Mg2+-dependent adenosine triphosphatase of sarcomplasmic reticulum were obtained from studies with primary cultures of rat skeletal muscle cells. Rates of synthesis at various stages of differentiation were estimated from the incorporation of tritium-labeled leucine into the ATPase. Cells were solubilized with detergent, and newly synthesized ATPase was isolated from cells by antibody precipitation in the presence of carrier ATPase. Radioactivity incorporated into the ATPase was determined after gel electrophoresis of the precipitates and counting of gel slices containing the ATPase band. In Dulbecco's modified Eagle's medium containing 10% horse serum and 0.5% chick embryo extract, mononucleated myoblast cells began to form multinucleated myotubes after about 50 hours in culture. Prior to fusion little ATPase synthesis was detectable; during fusion the ATPase was synthesized at an accelerating rate for a period of about 30 hours. The rate of synthesis levelled off after about 90 hours coincident with termination of fusion. In Dulbecco's modified Eagle's medium containing 20% fetal calf serum and 8% embryo extract, the onset of fusion was delayed for 30 to 40 hours. In this medium biosynthesis of the ATPase was also delayed so that biosynthesis of the ATPase appeared to be correlated with fusion of muscle cells. Cells cultured in Culbecco's modified Eagle's medium containgin 10% horse serum, but only 60 muM Ca2+, proliferated but did not fuse. Under these conditions, synthesis of the ATPase was measurable at 50 to 60 hours, and the rate of synthesis accelerated until 120 hours when it declined. Under all conditions degradation of the ATPase occurred with a half-life of 20 hours whereas the half-life of total protein degradation was 40 hours. Synthesis of the sarcoplasmic reticulum ATPase, like that of a number of other muscle-specific proteins, is greatly accelerated as myoblasts fuse and differentiate into myotubes. Fusion is not essential for this phenomenon, however, although it is normally concomitant with it.
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PMID:Assembly of the sarcoplasmic reticulum. Biosynthesis of the adenosine triphosphatase in rat skeletal muscle cell culture. 13 98

1. The effect was studied of local anesthetics (tetracaine, dibucaine, procaine and xylocaine) on the forward and the backward reactions of the calcium pump of skeletal muscle sarcoplasmic reticulum. 2. The inhibition of the rate of calcium uptake, the rate of calcium-dependent ATP splitting and the rate of calcium-dependent ATP-ADP phosphate exchange by sarcoplasmic reticulum in the presence of the above drugs is at least partially due to the inhibition of the phosphoprotein formation from ATP. 3. The rate of the ADP-induced calcium release from sarcoplasmic reticulum and the rate of ATP synthesis driven by the calcium efflux are inhibited on account of a reduction of the phosphoprotein formation by orthophosphate. 4. The phosphorylation of calcium transport ATPase by either ATP or orthophosphate is diminished by the local anesthetics owing to a reduction in the apparent calcium affinity of sarcoplasmic reticulum emmbranes on the outside and on the inside, respectively. 5. The drug-induced calcium efflux from calcium-preloaded sarcoplasmic reticulum vesicles, a reaction not requiring ADP, is probably not mediated by calcium transport ATPase.
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PMID:Aspects of the mechanism of action of local anesthetics on the sarcoplasmic reticulum of skeletal muscle. 13 47

The reversal of the calcium pump of cardiac sarcoplasmic reticulum (SR) prepared from dogs was investigated. Phosphorylation of the calcium transport ATPase by orthophosphate and ATP synthesis from ADP and orthophosphate by SR passively preloaded with calcium are demonstrated. The ADP-dependent calcium efflux from SR loaded with calcium in the presence of acetylphosphate is stoichiometrically coupled to ATP synthesis from ADP and orthophosphate.
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PMID:The reversal of the calcium pump of cardiac sarcoplasmic reticulum. 14 Jun 56

The (Ca2+ + Mg2+)-dependent ATPase (ATP phosphohydrolase, EC 3.6.1.3) from human erythrocytes occurred in two different states, A-state and B-state, depending on the membrane preparation. The A-state showed low maximum activity (V) and the Ca2+ activation was characterized by a Hill coefficient, nH, of about 1 and a Michaelis constant, KCa, about 30 micron. The B-state showed high V, a nH above 1, which indicates positive cooperativity of Ca2+ activation, and KCa of about 1 micron. With varying ATP concentrations, both the A-state and B-state showed negative cooperativity and slightly different values of Km. The B-state was shifted to A-state when the membranes were exposed to low Ca2+ concentration. The shift reached 50% at approx. 0.5 micron Ca2+. At the low Ca2+ concentrations an activator was released from the membranes. The A-state was shifted to the B-state when the membranes were exposed to Ca2+ in the presence of the activator. The shift reached 50% at about 30 micron Ca2+. The recovery of high V was time dependent and lasted several minutes. Increasing concentrations of Ca2+ and activator accelerated the recovery. It is suggested that the A-state and the B-state correspond to enzyme free of activator and enzyme associated with activator, respectively. Furthermore, the two states may respresent a resting and an active state, respectively, of the calcium pump.
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PMID:Reversible shift between two states of Ca2+-ATPase in human erythrocytes mediated by Ca2+ and a membrane-bound activator. 14 93

The effects of adenylyl methylene diphosphate (AMD), a non-hydrolyzable ATP analogue, were examined in sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle. The Ca2+-dependent APTase activity measured at 5 degrees C and pH 7.0 in 5.2 micrometer [gamma-32P]ATP and in the absence of added alkali metal salts was stimulated by added AMD. The steady state level of phosphoenzyme, however, was not decreased greatly by added AMP under these conditions. The hydrolysis of the phosphoenzyme formed at the steady state in the absence of added alkali metal salts was accelerated by added AMD to an extent that can account for the stimulation of the ATPase activity. At 5 degrees C and pH 7.0 the maximum stimulation of phosphoenzyme hydrolysis by AMD and the Km value for this ATP analogue were 4.3-fold and 40 micrometer, respectively. These results provide further support for our previous conclusion (Shigekawa, M., Dougherty, J.P. and Katz, A.M. (1978) J.Biol. Chem. 253, 1442--1450) that 2 classes of ATP site exist in the calcium pump ATPase in the absence of added alkali metal salts, one being the catalytic site and the other being the regulation site which activates the activity of the catalytic site.
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PMID:Stimulation of adenosine triphosphatase activity of sarcoplasmic reticulum by adenylyl methylene diphosphate. 15 52

Deuterium Fourier transform nuclear magnetic resonance (NMR) spectra at 34 MHz (corresponding to a magnetic field strength of 5.2 T) have been obtained of a variety of protein-lipid systems containing specifically deuterated phospholipids. The following systems were investigated as a function of temperature: sarcoplasmic reticulum ATPase (ATP phosphohydrolase, EC 3.6.1.3) complexed with 1-myristoyl-2-(14,14,14-trideuteriomyristoyl)-sn-glycero-3-phosphocholine (DMPC-d3) or 1,2-bis(16,16,16-trideuteriopalmitoyl)-sn-glycero-3-phosphocholine (DPPC-k6); human brain lipophilin complexed with DPPC-d6 or 1,2-bis(6,6-dideuteriopalmitoyl)-sn-glycero-3-phosphocholine (DPPC-6,6-d4); beef brain myelin proteolipid apoprotein (PLA) reconstituted with DMPC labeled as CD2 (or CD3) at one or more of positions 3, 4, 6, 8, 10, 12, or 14 of the sn-2 chain. For purposes of comparison, spectra were also obtained for bilayers containing cholesterol (CHOL). The results show that proteins either disorder or have little effect on hydrocarbon chain order in membranes above the gel to liquid-crystal phase transition temperature (Tc) of the pure lipids. Cholesterol, however, causes a very large ordering of the hydrocarbon chains above Tc, but both cholesterol and protein prevent chain crystallization (by effectively disordering chain packing) immediately below Tc. No evidence for any ordered "boundary lipid" in association with protein was found above Tc, perhaps due to the rough nature of protein surfaces. Above Tc, exchange between free bilayer and protein associated lipid is fast on the time scale of the deuterium NMR experiment (greater than or similar to 10(3) s-1). We have also obtained proton-decoupled phosphorus-31 nuclear magnetic resonance spectra at 60.7 MHz (corresponding to a magnetic field strength of 3.5 T) of DMPC, DMPC-AT-Pase, and DMPC-CHOL complexes. The results indicate that ATPase and CHOL CAUSE SMALL DECREASES IN 31P chemical shielding anisotropies but that in addition ATPase causes a four- to fivefold increase in 31P spin-lattice and Carr-Purcell spin-spin relaxation rates, suggesting the possibility of polar group protein-lipid interaction leading to increased correlation times in the region of the lipid phosphate head group.
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PMID:Protein-lipid interactions. A nuclear magnetic resonance study of sarcoplasmic reticulum Ca2,Mg2+-ATPase, lipophilin, and proteolipid apoprotein-lecithin systems and a comparison with the effects of cholesterol. 16 Feb 47


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