Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The (Na+ +K+)-activated, Mg2+-dependent ATPase from rabbit kidney outer medulla was prepared in a partially inactivated, soluble form depleted of endogenous phospholipids, using deoxycholate. This preparation was reactivated 10 to 50-fold by sonicated liposomes of phosphatidylserine, but not by non-sonicated phosphatidylserine liposomes or sonicated phosphatidylcholine liposomes. The reconstituted enzyme resembled native membrane preparations of (Na+ +K+)-ATPase in its pH optimum being around 7.0, showing optimal activity at Mg2+:ATP mol ratios of approximately 1 and a Km value for ATP of 0.4 mM. Arrhenius plots of this reactivated activity at a constant pH of 7.0 and an Mg2+: ATP mol ratio of 1:1 showed a discontinuity (sharp change of slope) at 17 degrees C, with activation energy (Ea) values of 13-15 kcal/mol above this temperature and 30-35 kcal below it. A further discontinuity was also found at 8.0 degrees C and the Ea below this was very high (greater than 100 kcal/mol). Increased Mg2+ concentrations at Mg2+:ATP ratios in excess of 1:1 inhibited the (Na+ +K+)-ATPase activity and also abolished the discontinuities in the Arrhenius plots. The addition of cholesterol to phosphatidylserine at a 1:1 mol ratio partially inhibited (Na+ +K+)-ATPase reactivation. Arrhenius plots under these conditions showed a single discontinuity at 20 degrees C and Ea values of 22 and 68 kcal/mol above and below this temperature respectively. The ouabain-insensitive Mg2+-ATPase normally showed a linear Arrhenius plot with an Ea of 8 kcal/mol. The cholesterol-phosphatidylserine mixed liposomes stimulated the Mg2+-ATPase activity, which now also showed a discontinuity at 20 degrees C with, however, an increased value of 14 kcal/mol above this temperature and 6 kcal/mol below. Kinetic studies showed that cholesterol had no significant effect on the Km values for ATP. Since both cholesterol and Mg2+ are known to alter the effects of temperature on the fluidity of phospholipids, the above results are discussed in this context.
 ...
PMID:Alterations in phospholipid-dependent (Na+ +K+)-ATPase activity due to lipid fluidity. Effects of cholesterol and Mg2+. 0 90

Adenosine 5'-triphosphate (ATP) synthesis driven by an artificially imposed membrane potential in right-side-out membrane vesicles of Escherichia coli was investigated. Membrane vesicles prepared in the presence of adenosine diphosphate were loaded with K+ by incubation with 0.5 M potassium phosphate. Addition of valinomycin resulted in the synthesis of 0.2 to 0.3 nmol of ATP/mg of membrane protein, whereas no synthesis was observed after addition of nigericin. Addition of K+, dicyclohexylcarbodiimide, carbonylcyanide p-trifluoromethoxyphenylhydrazone, or azide to the assay buffer inhibited ATP synthesis. Adenosine diphosphate and Mg2+ were found to be required. Ca2+, which can replace Mg2+ for the hydrolytic activity of the Mg2+-adenosine triphosphatase (ATPase) (EC 3.6.1.3), could not replace Mg2+ in the synthetic reaction and, in fact, inhibited ATP synthesis even in the presence of Mg2+. Strain NR-70, a mutant lacking the Mg2+-ATPase, was unable to synthesize ATP using an artificially imposed membrane potential. Additionally, the Mg2+-ATPase was found to contain tightly bound ATP.
 ...
PMID:Adenosine 5'-triphosphate synthesis energized by an artificially imposed membrane potential in membrane vesicles of Escherichia coli. 0 30

(Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) was purified from human cadaver renal tissue and exhibited a linear reaction rate with time. 100 g of whole kidney would yield 1--3.5 mg protein with a specific activity of 50--200 mol - kg-1 - h-1 for (Na+ + K+)-ATPase. The preparation was completely inhibited by 100 micronM ouabain with a Ki of 1.8 micronM. K+-dependent phosphatase increased during purification of (Na+ + K+)-ATPase to 7.8 mol - kg-1 - h-1. There was no detectable Mg2+-ATPase in the final preparation. Sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis yielded three protein peaks of 117 000, 92 500, and 56 000 daltons. The peptide band corresponding to 92 500 daltons underwent an Na+-dependent phosphorylation with [gamma-32P]-ATP. The band at 56 000 daltons stained for glycoprotein. The Km for ATP was 0.38 mM and that for Mg2+ was 0.5 mM. The formation of ADP and inorganic phosphate from ATP was stoichiometric. The Km for Na+ in the presence of 20 mM K+ was 16 mM and the Km for K+ in the presence of 100 mM Na+ was 1.5 mM. The temperature optimum was 51degrees C and the pH optimum was 7.0. (Na+ + K+)-ATPase in whole homogenate, microsomes, and NaI-treated microsomes exhibited a slowing of reaction rate (non-linearity) with time such that the enzyme was inactive by 10--15 min of reaction. This non-linearity was eliminated during purification. The significance is discussed.
 ...
PMID:Purification of the (Na+ + K+)-adenosine triphosphatase from human renal tissue. 1 1

In sarcoplasmic reticulum of rabbit skeletal muscles the activity of Ca2+, Mg2+- dependent ATPase was distinctly inhibited under effect of neuroleptic drugs - derivatives of phenothiazine and butyrophenone. The effect of tricyclic antidepressants was less pronounced. Tranquilizers (derivatives of 1,4-benzodiazepine) inhibited the enzyme, but trioxazin was only slightly active. High concentrations of lithium salts and of psychostimulants caffeine and corasole were found to stimulate the Ca2+, Mg2+-ATPase activity; low concentrations of the substances slightly inhibited the enzyme. The blocking effect of psychotropic drugs was more distinct, if the enzyme preparations were previously treated with ATP.
 ...
PMID:[Effect of psychotropic preparations on the activity of Ca- and Mg-dependent ATPase of the sarcoplasmic reticulum]. 1

A comparative study was performed for actomyosin complexes of the female rabbit myometrium in the state of labour (actomyosin of the control) and secondary uterine inertia (actomyosin of the model). Under the secondary uterine inertia the activity of actomyosin Ca2+- and Mg2+-ATPase decreases. When pH of the medium changes, ATPase of control actomyosin has two peaks of the activity: at rH 6.0 and pH 9.0, that of the model at pH 6.0. Actomyosin of the model and control differs by a degree and rate of superprecipitation, thermal stability and structure. It is supposed that the structural changes in actomyosin under the secondary uterine inertia occur due to accumulation of the metabolism products, the level of which with this pathology is beyond the limits of the adaptation potentialities of the organism.
 ...
PMID:[ATPase activity and fluorescence of myometrial actomyosin in experimental uterine inertia]. 1 9

Human skin fibroblasts, grown to confluency in the presence of 32P for random labelling of the phospholipids, showed upon 24 h incubation in the presence of either 8 mM L-serine or 4 mM ethanolamine an increased content of phosphatidylserine (150% of control cells) or phosphatidylethanolamine (116% of control cells), respectively. Concomitantly the phosphatidylcholine correspondingly decreased. Upon cell harvesting and gentle enzyme preparation the base-treated cells demonstrated a significantly higher unstimulated, fluoride- and thyrotropin-stimulated activity of adenylate cyclase. The activities of total ATPase, ouabain-sensitive ATPase, 5'-nucleotidase and gamma-glutamyltransferase remained unaltered. When subjecting enzyme preparations from fibroblasts to ultrasonication the activity of adenylate cyclase decreased progressively with energy applied, whereas the activities of the other enzymes were unaltered ((K+ + Na+)-ATPase, 5'-nucleotidase) or even increased (Mg2+-ATPase, gamma-glutamyltransferase). The results have a bearing upon the regulatory function of the phospholipid microenvironment of membrane-bound enzymes.
 ...
PMID:The influence of changes in the phospholipid pattern of intact fibroblasts on the activities of four membrane-bound enzymes. 1 85

Properties of HCO--3-stimulated ATPase from rat heart muscle nuclei were studied. The maximal activity of HCO--3-ATPase was observed at concentration of bicarbonate 25 mM. The enzyme had a pH optimum at pH 8.0-8.5. Bicarbonate stimulated the ATPase activity only in presence of Mg2+, Mn2+ and Zn2+, Co2+, Cd2+ and Ca2+ were ineffective. NaCO3 and Na2SO3 at concentration 30 mM stimulated the nuclear ATPase activity by 20% and 81%, respectively. Anions N3--, scn--, clO--4, and I-- inhibited both Mg2+-ATPase and HCO--3-ATPase. HSO--3 and SO2--4 ions did not affect the nuclear ATPase activity.
 ...
PMID:[Anion-sensitive nuclear ATPase of the rat heart]. 2 54

The activity of ATPase was studied in highly purified rat liver and thymus cell nuclei, HCO3-, CO3(2-) and SO3(2-) stimulated nuclear ATPase in 1.5--2 times. HSO3- did not affect the enzyme activity, and NO3-, J-, ClO4-,F- and SCN- inhibited it. Bicarbonate increased V and decreased Ka for ATP. SCN- inhibited HCO3--ATPase activity non-competitively with respect to HCO3-. Mg2+-ATPase activity did not depend on pH, and HCO3-component of the activity was decreased under alkaline pH. Mg2+, Mn2+ and Co2+ increased the initial ATPase activity and helped its stimulation with HCO3-. Ba2+, Ni2+ and Zn2+ inhibited the ATPase activity, and Ca2+ did not affect it, Nuclear ATPase is sensitive to 2,4-dinitrophenol and DNAase. It is suggested that cell nuclei have their own H+-ATPase differing for some characteristics from mitochondrial H+-ATPase.
 ...
PMID:[Investigation of adenosinetriphosphatase activity of rat liver and thymus cell nuclei]. 3 23

A plasma membrane-enriched fraction was prepared from homogenized rat pancreatic islets by a one-step sucrose gradient centrifugation. Using 125I-wheat germ agglutinin as a plasma membrane probe, a fraction was obtained at a sucrose density of about 1.10 that was enriched in 5'-nucleotidase, Mg2+-ATPase and alkaline phosphatase. The fraction contained little, if any, monoamino oxidase activity, insulin or DNA. Hydrolysis of 3-0-methyl-fluoresceinphosphate was stimulated by K+ (10mM) at a pH optimum of pH 8.2. Hydrolysis of ATP-gamma-32P in the presence of MgCl2 was of high specific activity and was optimum at pH 7.0 and 8.2. K+ did not affect ATP-hydrolysis. At pH 8.2, a small fraction of the total Mg2+-ATPase activity was inhibited by ouabain in the presence of Na+ and K+. Since K+-stimulated phosphatase activity does not correlate with Mg2+-ATPase, the two assay systems define separate enzymatic processes.
 ...
PMID:Cation-dependent phosphatase activites in a rat pancreatic islet plasma membrane fraction prepared by one-step gradient centrifugation. 3 53

Freshly isolated sarcoplasmic reticulum vesicles contain 0.05 mol of tightly bound ADP and 0.03 mol of tightly bound ATP per mol of Ca2+, Mg2+-ATPase (ATP phosphohydrolase, EC 3.6.1.3). These values were increased to 0.1-0.2 mol ADP and 0.2-0.3 mol ATP per mol of ATPase after incubation of vesicles in the presence of MgATP and Ca2+ at 25 degrees C and pH 7.0. Half-maximal enrichment of tightly bound nucleotides was obtained with 2.5 mM ATP and 0.32 microM free Ca2+. Uncoupling of calcium transport from ATPase activity by mild acidic conditions or with ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid at pH 7.0 decreased the ability of the membranes to be enriched with tightly bound nucleotides and also decreased the content of tightly bound nucleotides of previously enriched membranes. Tightly bound [3H]nucleotides could only be partially displaced by reincubation under enrichment conditions. Tightly bound nucleotides are associated with energized calcium translocation but do not appear to be directly involved in the catalytic cycle.
 ...
PMID:Occurrence and role of tightly bound adenine nucleotides in sarcoplasmic reticulum of rabbit skeletal muscle. 4 Feb 28


1 2 3 4 5 6 7 8 9 10 Next >>