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:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A method was developed to isolate renal basolateral membranes from cortical kidney tubule cells of single rats. The isolated membrane fraction was characterized by the measurement of marker enzyme activities and by electron microscopy. 1. After centrifugation of crude plasma membranes on a discontinuous sucrose density gradient the basolateral membranes accumulated at a sucrose density of p= 1.14-1.15 g/ml. The yield was 147 mug membrane protein/g kidney wet weight. Protein recovery was 0.1%. 2. (Na+ + K+)-ATPase was enriched 22-fold from the homogenate. The recovery was 2.6%. The (Na+ + K+)/Mg2+-ATPase ratio was 4.1. 3. The contamination by brush borders was small. Alkaline phosphatase was 1.6-fold enriched and 0.2% was recovered. Aminopeptidase was 1-fold enriched with a recovery of 0.1%. The contamination by mitochondria, lysosomes and endoplasmic reticulum was negligible. 4. In electron micrographs the basolateral membranes showed a typical triple layered profile and were characterized by the presence of junctional complexes, gap junctions or tight junctions.
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PMID:Isolation of the basal and lateral plasma membranes of rat kidney tubule cells. 13 91

Actin, myosin, and a high molecular weight actin-binding protein were purified from chronic myelogenous leukemia (CML) leukocytes. CML leukocyte actin resembled skeletal muscle and other cytoplasmic actins by its subunit molecular weight, by its ability to polymerize in the presence of salts, and to activate the Mg2+-ATPase activity of rabbit skeletal muscle myosin. CML leukocyte myosin was similar to other vertebrate cytoplasmic myosins in having heavy chains and two light subunits. However, its apparent heavy-chain molecular weight and Stokes radius suggested that it was variably degraded during purification. Purified CML leukocyte myosin had average specific EDTA- AND Ca2+-activated ATPase activities of 125 and 151 nmol Pi released/mg protein per min, respectively and low specific Mg2+-ATPase activity. The Mg2+-ATPase activity of CML myosin was increased 200-fold by rabbit skeletal muscle F-actin, but the specific activity relative to that of actin-activated rabbit skeletal muscle myosin was low. CML leukocyte myosin, like other vertebrate cytoplasmic myosins, formed filaments in 0.1 M KCl solutions. Reduced and denatured CML leukocyte-actin-binding protein had a single high molecular weight subunit like a recently described actin-binding protein of rabbit pulmonary macrophages which promotes the polymerization and gelation of actin. Cytoplasmic extracts of CML leukocytes prepared with ice-cold 0.34-M sucrose solutions containing Mg2+-ATP, dithiothreitol, and EDTA at pH 7.0 underwent rapid gelation when warmed to 25 degrees C. Initially, the gel could be liquified by cooling to ice-bath temperature. With time, warmed cytoplasmic extract gels shrunk ("contracted") into aggregates. The following findings indicated that CML leukocyte actin-binding protein promoted the temperature-dependent gelation of actin in the cytoplasmic extracts and that CML leukocyte myosin was involved in the contraction of the actin gels: (a) Cytoplasmic extract gels initially contained actin as their major polypeptide component and consistent of tangled thin filaments; (b) Contracted aggregates of cytoplasmic extract gels contained by large quantities of myosin as well as actin; (c) Purified actin-binding protein underwent a temperature-dependent, reversible aggregation and caused low concentrations of purified muscle or CML leukocyte actins to gel in sucrose solutions; (d) The gels formed from purified actin plus purified actin-binding protein slowly contracted in the presence but not in the absence of purified CML leukocyte myosin; (e) Rabbit antiserum against purified CML leukocyte actin-binding protein but not against purified CML leukocyte myosin inhibited the gelation of warmed CML leukocyte extracts. Antiserum against CML leukocyte myosin had no effect on the gelation of CML leukocyte extracts but partially curtailed the contraction of the CML leukocyte extract gels and of gels formed from purified CML leukocyte actin-binding protein plus rabbit skeletal muscle actin.
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PMID:Interactions of actin, myosin, and an actin-binding protein of chronic myelogenous leukemia leukocytes. 13 21

1. The activities of some membrane-bound enzymes such as adenylate cyclase, Na+ + K+-stimulated adenosine triphosphatase (Na+ + K+-ATPase), Ca2+-stimulated ATPase and Mg2+-stimulated ATPase were examined in heart sarcolemmal fractions from control and cardiomyopathic hamsters at different stages of heart failure. 2. The basal adenylate cyclase activity in sarcolemma from cardiomyopathic animals with early, moderate and late stages of heart failure was not different from the control values whereas the sodium fluoride- and catecholamine-stimulated adenylate cyclase activities were depressed in cardiomyopathic sarcolemma at moderate and late stages. 3. The sarcolemmal Na+ + K+-ATPase activity was decreased and the non-specific phosphatase activity was increased at early, moderate and late stages of heart failure. 4. The sarcolemmal Ca2+-ATPase activity was decreased at moderate and late stages whereas the Mg2+-ATPase activity was decreased at the late stages of heart failure only. 5. A marked decrease was found in calcium binding by heart sarcolemma from cardiomyopathic hamsters at late stages of failure. 6. These results suggest that dramatic sarcolemmal changes are associated with heart failure, and support the view that membrane abnormalities play a crucial role in the development of myocardial dysfunction, cyclase, calcium binding, heart failure, heart membranes, sarcolemmal enzymes.
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PMID:Comparison of heart sarcolemmal enzyme activities in normal and cardiomyopathic (UM-X7.1) hamsters. 13 61

The Wachstein-Meisel ATPase histochemical method has been previously used to demonstrate the ultrastructural localization of this enzyme in both whole liver and isolated plasma membranes following fixation in glutaraldehyde. In the present study biochemical assay, of liver plasma membrane enzymes following fixation in cold 2.5% glutaraldehyde showed that approximately 40% of Mg2+-ATPase, but only 4% of (Na+-K+)-ATPase activity remained in membranes from either control or ANIT-treated rats. In addition, 5'-nucleotidase activity was almost abolished by fixation. The present results indicate that the Wachstein-Meisel method, when applied to biliary canaliculi, can reliably be used to demonstrate the ultrastructural, histochemical localization of Mg2+-ATPase but not that of (NA+-K+)-ATPase. Furthermore, the method permits a valid comparison to be made of the relative Mg2+-ATPase activity in normal and chemically damaged biliary canaliculi.
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PMID:Liver plasma membrane enzyme activities following glutaraldehyde fixation. 13 43

The total Mg2+-ATPase and Na+, K+-ATPase activity was studied in the fractions of "400 g X for 20 min" and "900 g X for 30 min" conditionally called the fraction of the external cellular membranes and total fraction of mitochondria. The subcellular fractions were isolated from great hemispheres and stem part of the rat brain. The brain of control animals and those during a severe spasmodic attact induced by the oxygen action at a pressure of 6 ati was studied. The total ATPase activity is established to be practically the same in the studied brain areas and unchanged with hyperoxia. Hyperoxia accompanying by convulsions results in an increase in the activity of Mg2+-ATPase and in a decrease in that of Na+, K+-ATPase both in the cerebral cortex and the stem part. The authors suppose that the decrease in the enzyme activity may occur due to an inhibitory effect on it of the lipids reoxidation products formed in the brain with hyperoxia.
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PMID:[ATPase activity of subcellular rat brain fractions following hyperoxia]. 13 79

A highly purified preparation of myosin from Physarum polycephalum has been shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis to contain heavy chains and only one molecular weight class of light chains, of approx. 15 000 daltons. Kinetic investigations of the Ca2+-ATPase and Mg2+-ATPase (ATP phosphohydrolases, EC 3.6.1.3) at pH 8.0 gave Km and V values of 17.3 muM and 1.25 mumol Pi/min per mg, and 2.4 muM and 0.12 mumol Pi/min per mg, respectively. Adenylyl imidodiphosphate, a beta-gamma-imido ATP analog, inhibited the ATPase activity of Physarum myosin competitively with Ki values equal to 350 and 12 muM in the presence of Ca2+ and Mg2+, respectively. The ATPase activity of Physarum myosin was inhibited at a very low rate (t1/2 = 24 h) by the ATP analog, 6,6'-dithiobis(inosinyl imidodiphosphate), with concentrations of inhibitor previously shown to inactivate (t1/2 approximately 10 min) skeletal and cardiac myosins rapidly by reacting with key cysteines.
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PMID:Observations on the kinetics, subunit composition, and sulfhydryl reactivity of myosin from Physarum polycephalum. 13 51

To determine whether choleretic infusions of bile acids modified the function or structure of the membrane of the bile canaliculus, sodium taurocholate (NaTc) or dehydrocholate (DHC) was infused into male rats at a rate of 80 mumoles per hour over an 18-hour period. Bile was collected by fistula and phospholipid and cholesterol content was measured in bile, liver homogenates, and isolated liver plasma membranes (LPM) enriched in bile canaliculi. Na+, K+-ATPase, Mg2+-ATPase, 5'-nucleotidase, and alkaline phosphatase activities were also measured in LPM. NaTc infusions enhanced cholesterol and phospholipid output in the bile in association with a significant increase in phospholipid in both LPM and liver homogenate. Although DHC infusions resulted in a comparable excretion of bile acid, phospholipid and cholesterol output in bile did not increase from control values and the concentration of these lipids in LPM and liver homogenate also did not change. However, LPM Na+, K+-ATPase significantly increased after DHC infusions compared to NaTc-infused animals or controls. Neither bile acid altered the activities of Mg2+-ATPase, 5'-nucleotidase, or alkaline phosphatase. Both bile acids increased the diameter of the lumen of the bile canaliculus as assessed by scanning electron microscopy and produced irregularities and outpouchings in the canalicular membrane. Diverticuli and loss of microvilli were most prominent with DHC infusions whereas canalicular side branching and the density of microvilli, either remained unchanged or increased following NaTc infusions. Although the morphologic findings are qualitative, the results of these studies indicate that chronic choleretic infusions of NaTc and DHC have divergent effects, not only on enzyme activities in liver plasma membrane, but on phospholipid composition and 3-dimensional structure. These findings suggest that bile acids may after biliary secretion not only through their osmotic effects, but by modifying lipids and enzymes in the membrane of the bile canaliculus.
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PMID:Effects of chronic choleretic infusions of bile acids on the membrane of the bile canaliculus. A biochemical and morphologic study. 13 67

The effect of the hallucinogenic drug harmaline was tested on rat kidney proximal tubular solute and water transport, using in vivo micropuncture and electrophysiological techniques as well as in vitro biochemical techniques. During peritubular application harmaline (5 mmol/l) was found to block net tubular volume absorption reversibly (by 85%) through inhibition of active Na+ transport and possibly active HCO-3 transport. The inhibition was accompanied by a rapid strong depolarization of the tubular cell membranes. As a biochemical equivalent harmaline inhibited the Na+-K+-ATPase and the Mg2+-ATPase of peritubular cell membrane fractions as well as the HCO-3-stimulated ATPase of a brush border membrane fraction with similar kinetics. By studying glucose tracer efflux and by measuring cell membrane potential and conductance changes in response to glucose perfusions, no evidence for a direct effect of harmaline on Na+-glucose (or amino acid) cotransport mechanisms in the brush border could be obtained. The data suggest that harmaline does not specifically compete with Na+ for transport sites. Neither are the cotransport systems in the brush border membrane specifically inhibited, nor could the inhibition of the Na+ pump in the peritubular cell membrane simply result from a competition between harmaline and Na+.
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PMID:The mechanism of action of harmaline on renal solute transport. 14 Mar 66

Oviductal secretions include an ATPase (EC 3.6.1.3) that is transferred from the outer surface of the secretory cells to the surface of the ovulated oocyte. The enzyme has been purified and is a highly labile, very high molecular weight lipoprotein complex (greater than 4-10(6)). It consists of 47% protein and 53% lipid. Lipid composition is limited to phosphatidylcholine, phosphatidylethanolamine and sphingomyelin. The basic protein subunit has a molecular weight of 170 000. The enzyme exhibits many of the characteristics of ectoenzyme ATPase. The enzyme is Mg2+ or Ca2+ dependent; the Mg2+-ATPase has pH optima at 6.0 and 7.8 and the Ca2+-ATPase at 9.0. Substrate specificity is limited to ATP with lesser activity towards GTP, CTP, UPT and ADP. Km for ATP is 0.88 mM and the enzyme is inhibited at substrate concentrations greater than 3 mM ATP.
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PMID:Purification and characterization of an extracellular ATPase from oviductal secretions. 14 Jul 3

Myosin and paramyosin have been purified from the nematode, Caenorhabditis elegans. The properties of the myosin in general resemble those of other myosins. The native molecule is a dimer of heavy (210,000 dalton) polypeptide chains and contains 18,000 and 16,000 dalton light chains. When rapidly precipitated from solution, it forms small, bipolar aggregates, about 150 nm long, consistent with the expected molecular structure of a rigid rod with a globular head region at one end. Its ATPase activity is stimulated by Ca2+ and EDTA. The myosin binds to F actin in a polar and ATP-sensitive manner, and the Mg2+-ATPase is activated by either F actin or nematode thin filaments. Dialysis of myosin to low ionic strength produces very long filaments. When a myosin-paramyosin mixture is dialyzed under the same condtions, co-filaments form which consist of a myosin cortex, surrounding a paramyosin core. Some properties of myosin from the mutants E675 and E190, which have functionally and structurally altered body wall muscles, are compared with those of wild-type myosin. These myosins of these results are discussed in terms of the myosin heavy chain composition.
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PMID:Myosin and paramyosin of Caenorhabditis elegans: biochemical and structural properties of wild-type and mutant proteins. 14 Jul 64


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