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)

Studies into the activity of adenosine triphosphatase (ATPase) in homogenates of liver, cerebral cortex, renal cortex, and mucosa of small intestine of swine have shown differentiated activity patterns, with peak activity developing in the liver. This has been related to a particularly high metabolism performance of the liver in fattening pigs. No difference was found to exist between magnesium activation of ATPase of swine tissue homogenates and that in tissue obtained from ruminants. ATPase which could be activated by sodium and potassium ions and inhibited by ouabain was detectable from cerebral and renal cortex. Sodium and potassium ATPases accounts from some 25 per cent of the total activity. ATPase that could be stimulated by calcium ions was recorded only from liver homogenate. The optimum pH values of ATPase were between 7.5 and 8 in the liver, 9 in mucosa of small intestine, and 9.5 in cerebral and renal cortex.
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PMID:[The activity and properties of adenosine triphosphatase in various swine organs (liver, cerebral and kidney cortex, small intestinal mucosa)]. 1 Aug 70

1. Guanylate cyclase of every fraction studied showed an absolute requirement for Mn2+ ions for optimal activity; with Mg2+ or Ca2+ reaction was barely detectable. Triton X-100 stimulated the particulate enzyme much more than the supernatant enzyme and solubilized the particulate-enzyme activity. 2. Substantial amounts of guanylate cyclase were recovered with the washed particulate fractions of cardiac muscle (63-98%), skeletal muscle (77-93%), cerebral cortex (62-88%) and liver (60-75%) of various species. The supernatants of these tissues contained 7-38% of total activities. In frog heart, the bulk of guanylate cyclase was present in the supernatant fluid. 3. Plasma-membrane fractions contained 26, 21, 22 and 40% respectively of the total homogenate guanylate cyclase activities present in skeletal muscle (rabbit), cardiac muscle (guinea pig), liver (rat) and cerebral cortex (rat). In each case, the specific activity of this enzyme in plasma membranes showed a five- to ten-fold enrichment when compared with homogenate specific activity. 4. These results suggest that guanylate cyclase, like adenylate cyclase, and ouabain-sensitive Na+ + K+-dependent ATPase (adenosine triphosphatase), is associated with the surface membranes of cardiac muscle, skeletal muscle, liver and cerebral cortex; however, considerable activities are also present in the supernatant fractions of these tissues which contain very little adenylate cyclase or ouabain-sensitive Na+ + K+-dependent ATPase activities.
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PMID:Guanylate cyclase. Subcellular distribution in cardiac muscle, skeletal muscle, cerebral cortex and liver. 1 Aug 90

To define the mechanism responsible for the slow rate of calcium transport by cardiac sarcoplasmic reticulum, the kinetic properties of the Ca2+-dependent ATPase of canine cardiac microsomes were characterized and compared with those of a comparable preparation from rabbit fast skeletal muscle. A phosphoprotein intermediate (E approximately P), which has the stability characteristics of an acyl phosphate, is formed during ATP hydrolysis by cardiac microsomes. Ca2+ is required for the E approximately P formation, and Mg2+ accelerates its decomposition. The Ca2+ concentration required for half-maximal activation of the ATPase is 4.7 +/- 0.2 muM for cardiac microsomes and 1.3 +/- 0.1 muM for skeletal microsomes at pH 6.8 and 0 degrees. The ATPase activities at saturating concentrations of ionized Ca2+ and pH 6.8, expressed as ATP hydrolysis per mg of protein, are 3 to 6 times lower for cardiac microsomes than for skeletal microsomes under a variety of conditions tested. The apparent Km value for MgATP at high concentrations in the presence of saturating concentrations of ionized Ca2+ is 0.18 +/- 0.03 ms at pH 6.8 and 25 degrees. The maximum velocity of ATPase activity under these conditions is 0.45 +/- 0.05 mumol per mg per min for cardiac microsomes and 1.60 +/- 0.05 mumol per mg per min for skeletal microsomes. The maximum steady state level of E approximately P for cardiac microsomes, 1.3 +/- 0.1 nmol per mg, is significantly less than the value of 4.9 +/- 0.2 nmol per mg for skeletal microsomes, so that the turnover number of the Ca2+-dependent ATPase of cardiac microsomes, calculated as the ratio of ATPase activity to the E approximately P level is similar to that of the skeletal ATPase. These findings indicate that the relatively slow rate of calcium transport by cardiac microsomes, whem compared to that of skeletal microsomes, reflects a lower density of calcium pumping sites and lower Ca2+ affinity for these sites, rather than a lower turnover rate.
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PMID:Calcium transport ATPase of canine cardiac sarcoplasmic reticulum. A comparison with that of rabbit fast skeletal muscle sarcoplasmic reticulum. 1 Dec 10

The brush border of intestinal epithelial cells consists of an array of tightly packed microvilli. Within each microvillus is a bundle of 20-30 actin filaments. The basal ends of the filament bundles are embedded in and interconected by a filamentous meshwork, the terminal web, which lies directly beneath the microvilli. When calcium and ATP are added to isolated brush borders that have been treated with the detergent, Triton X-100, the microvillar filament bundles rapidly retract into and through the terminal web region. Biochemical studies of brush border contractile proteins suggest that the observed microvillar contraction is actomyosin mediated. We have shown previously that the major protein of the brush border's actin (Tilney, L. G., and M. S. Mooseker. 1971. Proc. Natl. Acad. Sci. U. S. A. 68:2611-2615). The brush border also contains a protein with the same molecular weight as the heavy chain subunit of myosin (200, 000 daltons). In addition, preparations of demembranated brush borders exhibit potassium-EDTA ATPase activity of 0.02 mumol phosphate/mg-min (22 degrees C); this assay is diagnostic for myosin-like ATPase isolated from vertebrate sources. Other proteins of the brush border include a 30,000 dalton protein with properties similar to those of tropomyosin, and a protein with the same molecular weight as the Z band protein, alpha-actinin (95,000 daltons). How these observations bear on the basis for microvillar movements in vivo is discussed within the framework of our recent model for the organization of actin and myosin in the brush border (Mooseker, M. S., and L. G. Tilney. 1975. J. Cell Biol. 67:725-743).
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PMID:Brush border motility. Microvillar contraction in triton-treated brush borders isolated from intestinal epithelium. 1 Dec 22

Sarcoplasmic reticulum (SR) isolated from rat aorta exhibited ATP dependent Ca2+ uptake in the presence of Mg2+. The maximum capacity and apparent binding constant were 23n moles/mg and 1.8 X 10(4) M (-1), respectively. The energy source of this active Ca2+ accumulation would be Mg-ATPase associated with the membrane. Ca2+ which was taken up inside of sarcoplasmic reticulum was released rapidly by washout with the medium containing no Ca2+. These facts suggest that sarcoplasmic reticulum in vascular smooth muscle cell may play and important role in the regulation of intracellular Ca2+ concentration.
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PMID:Calcium uptake, release and Mg-ATPase activity of sarcoplasmic reticulum from arterial smooth muscle. 1 59

Some of the characteristics of the pyrophosphatase and ATPase activities studied in isolated cartilage matrix vesicles were found to be similar to those already reported for the solubilized and purified bone alkaline phosphatase. Thus, the pH optimum of the pyrophosphatase activity responded similarly to changes in the concentration of Mg2+, Ca2+, and PPi. Further, the ATPase activity was not activated by Ca2+ in the presence of an optimal Mg2+ concentration. It is proposed that a function of the alkaline phosphatase of matrix vesicles in vivo is to hydrolyze the substrates PPi, ADP, and ATP, which are known inhibitors of calcium phosphate precipitation.
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PMID:Pyrophosphatase and ATPase of isolated cartilage matrix vesicles. 1 78

Myosin was extracted and partially purified from the head portion of spermatozoa of the starfish, Asterias amurensis. The sperm myosin showed a specific Ca2+-activated ATPase [EC 3.6.1.3] activity of 0.2 mumoles Pi/min/mg at high ionic strength and pH 6.5. It resembled egg myosin in forming thick filaments, becoming attached to actin filaments. subunit composition, and serological properties.
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PMID:Isolation of myosin from starfish sperm heads. 1 47

Intact vacuoles were isolated from petals of Hippeastrum and Tulipa (Wagner G.J. and Siegelman, H.W. (1975) Science 190, 1298--1299). The ATPase activity of fresh vacuole suspensions was found to be 2--3 times that of protoplasts from the same tissue. 70--80% of the ATPase activity of intact vacuoles was recovered in tonoplast preparations. The antibiotic Dio-9 at 6mug/10(6) vacuoles or protoplasts causes 40% inhibition. However, only the protoplast ATPase is sensitive to oligomycin. N,N'-dicyclohexylcarbodiimide (DCCD) slightly stimulates ATPase activity in both vacuole and protoplast suspensions, whereas ethyl-3-(3-dimethylaminopropyl carbodiimide) (EDAC) strongly inhibits. Spectrophotometric studies show that in the petal the vacuolar contents have a pH of 4.0 for Tuplipa and 4.3 for Hippeastrum, whereas the intact isolated vacuole has an internal pH of 7.0 (in pH 8.0 buffer) for (Tulipa and about 7.3 for Hippeastrum. Internal ion concentrations of 150, 46, 30, 30 and 6 mM were found for K+, Na+, Mg2+, Cl-, and Ca2+ respectively, which are about the same as those in protoplasts.
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PMID:Membrane-bound ATPase of intact vacuoles and tonoplasts isolated from mature plant tissue. 1 30

A membrane fraction enriched in parathyroid hormone (PTH)-sensitive adenylate cyclase and sodium and potassium ion-activated (Na+, K+)-ATPase was prepared from bovine kidney. Tritiated PTH binding to this membrane fraction was dependent on both hormone and membrane protein concentration. Both total and specific binding of the hormone decreased significantly after 5 to 10 min of incubation at 22 degrees. PTH binding was highly specific, being sensitive to inhibition only with active forms of unlabeled hormone (native and 1-34 PTH). Specific binding showed a pH optimum of 7.3 to 7.5. Inhibition of binding of tritiated hormone by unlabeled PTH was also highly effective at pH 6.0, but this apparently specific binding was also inhibited by adrenocorticotropic hormone, insulin, glucagon, and vasopressin. Dissociation of bound hormone was demonstrated, and an apparent dissociation constant of 4.6 X 10(-2) min-1 was obtained. Specific binding was eliminated by pretreatment of the membranes with trypsin. The concentration dependence for inhibition of binding with unlabeled PTH was identical to that for activation of adenylate cyclase in this membrane preparation, and binding was also inhibited by concentrations of calcium in the 0.5 to 2 mM range.
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PMID:Binding of tritiated bovine parathyroid hormone to plasma membranes from bovine kidney cortex. 1 29

The effects of acid on fragmented sarcoplasmic reticulum from rabbit white skeletal muscle have been studied. Brief exposure of sarcoplasmic reticulum membranes to pH values in the range 5.5 to 6.0 at 37 degrees caused rapid inactivation of calcium accumulation measured at 25 degrees in the presence of oxalate (calcium uptake) while (Ca2+, Mg2+)-ATPase (EC 3.6.1.3) activity was enhanced by 75%. ATPase activity, measured at 37 degrees in the absence of oxalate and in the calcium steady state, was unaltered when calcium uptake was inactivated. Calcium efflux from sarcoplasmic reticulum vesicles, previously loaded passibely with 45CaCl2, was only slightly increased when calcium uptake was abolished. At still lower pH values, 5.0 to 5.5, (Ca2+, Mg2+)-ATPase was inactivated while Mg2+ ATPase was more acid-resistant. Acid inactivation of calcium uptake followed simple first order kinetics for at least 80% of the time course. The rate constant, k, increased from 0.043 min-1 to 1.63 min-1 between pH 6.50 and pH 5.35. At pH 4.65, Ea, the energy of activation, was 31 kcal mol-1 between 24 degrees and 43 degrees. Inactivation, once initiated, was irreversible. Aged suspensions of sarcoplasmic reticulum were more sensitive to acid inactivation. Ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid enhanced inactivation, and calcium specifically protected against inactivation with half-maximal effect at 1 to 2 mM. The sulfhydryl reagent, dithiothreitol (1 mM), caused significantly increased rates of inactivation. Calcium binding was studied by dual wavelength spectrophotometry and stopped flow analysis. Acid inactivation distinguished two ATP-induced binding sites, previously described (Entman, M. L., Snow, T. R., Freed, D., and Schwartz, A. (1973) J. Biol. Chem. 248, 7762-7772) as a superficial Mg2+-independent Site A which binds and releases calcium rapidly and a deeper Mg2+-dependent Site B which binds and releases calcium more slowly. Rates of binding to both sites were decreased by acid inactivation. Binding of calcium to Site A increased, however, from 4.6 to 6.4 nmol mg of protein-1 whereas that to Site B decreased from 17.0 to 6.9 nmol mg of protein-1. Passive binding of calcium to sites of medium affinity (K = 7 X 10(4) M-1) was unaffected by acid inactivation of calcium uptake. Temperature dependence of (Ca2+, Mg2+)-ATPase was unchanged in the range 9-34 degrees. Above 34 degrees, the higher activation energy process (Ealpha = 33.7 kcal mol-1) observed in control sarcoplasmic reticulum and thought to arise from a conformational change in the ATPase (Inesi, G., Millman, M., and Eletr, S. (1973) J. Mol. Biol. 81, 483-504) was diminished by acid inactivation (Ealpha = 8.2 kcal mol-1) in a manner suggesting that it is related to active calcium transport. The ATP in equilibrium 32Pi exchange reaction was diminished by acid, but 25% of the activity remained when calcium uptake was completely abolished...
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PMID:Proton inactivation of Ca2+ transport by sarcoplasmic reticulum. 1 42


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