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

---

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

The requirement of actual splitting of ATP for endocytosis in erythrocyte ghosts has been confirmed by use of the ATP analog, 5'-adenylylimidodiphosphate, (AMP-P(NH)P). This compound, in which the oxygen connecting the beta and gamma phosphorus atoms was replaced by an NH group, did not cause endocytosis nor was it a substrate for ATPase activity. AMP-P(NH)P was a competitive inhibitor both for the endocytosis and the Mg2+-ATPase activities. The K1 of AMP-P(NH)P for Mg2+ ATPase activity was 2.0 - 10-4 M and, while the Km of ATP for this activity was also 2.0 - 10-4 M indicating nearly identical affinities of ATP and AMP-P(NH)P for the active site. ADP, or ADP plus orthophosphate, did not cause endocytosis, showing that endocytosis was not due to binding of the products of ATP hydrolysis. Sodium or potassium ion or ouabain had no effect on endocytosis, which eliminated the possibility of involvement of the Na+, K+ ATPase in the endocytosis process. Calcium could not be substituted for magnesium; rather it inhibited endocytosis at the concentration of 1 - 10-3 M. EGTA relieved the inhibitory effect of Ca, which indicated that the binding of calcium to the membrane was reversible. These experimental results reaffirm the conclusion that ATP must be split to engender endocytosis under these conditions. Some characteristic parameters of the hemoglobin-free porcine erythrocyte ghosts were studied in order to characterize the system more adequately.
...
PMID:Energy-dependent endocytosis in erythrocyte ghosts. IV. Effects of Ca2+, Na+ +K+, and 5'-adenylylimidodiphosphate. 12 70

The ionic influence and ouabain sensitivity of lymphocyte mg-2+-atpase and Mg-2+-(Na+ +K+)-activated ATPase were studied in intact cells, microsomal fraction and isolated plasma membranes. The active site of 5'-nucleotidase and Mg2+-ATPase seemed to be localized on the external side of the plasma membrane whereas the ATP binding site of (Na+ +K+)-ATPase was located inside the membrane. Concanavalin A induced an early stimulation of Mg2+-APTase and (Na+ +K+)-ATPase both on intact cells and purified plasma membranes. In contrast, 5'-nucleotidase activity was not affected by the mitogen. Although the thymocyte Mg2+-ATPase activity was 3-5 times lower than in spleen lymphocytes, it was much more stimulated in the former cells (about 40 versus 20%). (Na+ +K+)-ATPase activity was undectectable in thymocytes. However, in spleen lymphocytes (Na+ +K+)-ATPase activity can be detected and was 30% increased by concanavalin A. Several aspects of this enzymic stimulation had also characteristic features of blast transformation induced by concanavalin A, suggesting a possible role of these enzymes, especially Mg2+-ATPase, in lymphocyte stimulation.
...
PMID:Effect of concanavalin A on membrane-bound enzymes from mouse lymphocytes. 12 86

Elaboration of a semiautomated kinetic test on LKB 8600 apparatus for ATPase is described, using the PK-LDH system. As optimal ionic conditions 3 mmol-1 - minus 1 potassium chloride and 100 mmol-1 - minus 1 sodium chloride are proposed for measurement of (Na+-K+)-ATPase activities of rat intestinal brush borders. NH+4 can substitute for K+. The coefficients of variation of the method are 2.4% for Mg2+-ATPase and 4.9% for (Na+-K+)-ATPase determinations.
...
PMID:Studies on intestinal adenosine triphosphatases. I. Application of a semiautomated method to the rat intestinal brush borders. 12 50

The reactivity of the sulfhydryl groups in myosin B to N-ethylmaleimide (NEM) was investigated under various conditions. Under the conditions where actin and myosin associate, i.e. at low ionic strength, only Mg2+-ATPase [EC 3.6.1.3] activity was markedly activated by NEM treatment, whereas coupling of EDTA-ATPase inhibition with Ca2+-ATPase activation, which was seen on blocking S1 of myosin A with NEM, was observed under conditions at which the dissociation of actomyosin occurs, i.e. at high ionic strength, suggesting the covering with actin of the S1 region of myosin. Nevertheless, APT accelerated the reactivity of S1 and S2 much more in the myosin B system than in myosin alone. NEM-modified myosin B ATPase exhibited a shift of the KCL dependence curve to high concentration, a shift of the maximum activation of ATPase activity to high Mg ion concentration and a suppression of substrate inhibition at high substrate concentrations. These all indicate that the blocking by NEM of Sa, the sulfhydryl group related to the activation of Mg2+-ATPase of myosin B, brings about an increase in the association of myosin and actin in the myosin B system, resulting in an activation of Mg2+-ATPase activity. In addition, the relationship between Sa and a sulfhydryl group(s) essential for Ca2+ sensitivity was discussed.
...
PMID:The sulfhydryl groups involved in the active site of myosin B adenosinetriphosphatase. I. Relantionship of the sulfhydryl group responsible for Mg2+-ATPase activation to the S1 and S2 groups. 12 48

We have partially purified active delta and epsilon subunits of the E. coli membrane-bound Mg2+-ATPase (ECF1). Treating purified ECF1 with 50% pyridine precipitates the major subunits (alpha, beta, and gamma) of the enzyme, but the two minor subunits (delta and epsilon), which are present in relatively small amounts, remain in solution. The delta and epsilon subunits were then resolved from one another by anion exchange chromatography. The partially purified epsilon strongly inhibits the hydrolytic activity of ECF1. The epsilon fraction inhibits both the highly purified five-subunit ATPase and the enzyme deficient in the delta subunit. The latter result indicates that the delta subunit is not required for inhibition by epsilon. By contrast, two-subunit enzyme, consisting chiefly of the alpha and beta subunits, was insensitive to the ATPase inhibitor, suggesting that the gamma subunit may be required for inhibition by epsilon. The partially purified delta subunit restored the capacity of ATPase deficient in delta to recombine with ATPase-depleted membranes and to reconstitute ATP-dependent transhydrogenase. Previously we reported (Biochem, Biophys. Res. Commun. 62:764 [1975]) that a fraction containing both the delta and epsilon subunits of ECF1 restored the capacity of ATPase missing delta to recombine with depleted membranes and to function as a coupling factor in oxidative phosphorylation and for the energized transhydrogenase. These reconstitution experiments using isolated subunits provide rather substantial evidence that the delta subunit is essential for attaching the ATPase to the membrane and that the epsilon subunit has a regulatory function as an inhibitor of the ATPase activity of ECF1.
...
PMID:Partial purification of active delta and epsilon subunits of the membrane ATPase from escherichia coli. 12 87

Concanavalin A inhibits the (Na+-K+)-ATPase activity of isolated rat-liver plasma membranes, while leaving the Mg2+-ATPase unaffected. Glucagon and cyclic AMP act supplementary to the lectin in the inhibition. The lectin effect is counteracted by insulin and L-epinephrine, and is completely abolished by the beta-adrenergic blocking agent propranolol. Results are discussed on the basis of the known interactions of concanavalin A with plasma membrane components, including its hormone-like action.
...
PMID:Studies on plasma membranes. XXIII. Hormone-like action of concanavalin A on liver plasma membranes: inhibition of (Na+-K+)ATPase. 12 72

Cardiomyopathic hamsters (UM-X7.1) show clinical signs of congestive heart failure and an abnormal EKG pattern. The sarcolemmal fraction obtained from the failing hearts at advanced stages of myopathy exhibited no change in the basal adenylate cyclase activity; however, the activity of this enzyme in the presence of catecholamines or NaF was lower in the failing heart sarcolemma than that in the control. The activities of Ca2+-ATPase, Mg2+-ATPase, and Na+-K+-ATPase in the failing heart sarcolemma were also less than the control values. These results suggest an association of membrane defect with heart failure.
...
PMID:Membrane alteration in failing hearts of cardiomyopathic hamsters. 12 77

Mg2+-dependent Ca2+-activated ATPase of microsoma fraction from the grey matter of cerebral great hemispheres determined after the preliminary treatment of the preparation with 0.1% digitonin, while preserved in the medium with 10 mM mercaptoethanol for seven days at a temperature of 4-6 degrees C is inactivated by 10-15% and approximately by 50% while preserved without mercaptoethanol. Mercaptoethanol does not make reactivating effect. SH-reagents at definite concentrations completely inhibit the activity of Mg2+, Ca2+-ATPase. Half-maximum inhibition of the enzyme is reached with the salirgan, p-CMB and NEM concentrations of 5-10(-6) M, 5-10(-6) M and 5-10(-3) M, respectively. Mg2+-ATPase is not suppressed completely, and at high concentrations of SH-reagents the residual activity is 1.3 muM of Pi per 1 mg of protein in 1 hr. ATP in the concentrations optimal for manifestation of Mg2+, Ca2+-ATPase (3 mM) efficiently protects the enzyme from the inactivating effect of NEM. This gives reasons to suppose that the active centre of Mg2+, Ca2+-ATPase contains an SH-group. The quantity of SH-groups readily accessible of the Ellman reactive in the initial preparation of the brain microsomes is 45 + 2.0 nM per 1 mg of protein and in the preparation dissolved in 2.5% sodium dodecyl sulphate, 110 + 7.8 nmM per 1 mg of protein. In the presence of 0.1% digitonin the quantity of SH-groups of the preparation is 55 + 3.5 nM per 1 mg of protein, simultaneously such treatment of detergent results in manifestation of Mg2+, Ca2+-ATPase activity. An inactivating effect of SH-reagents and the protective effect of ATP indicate similarity of the enzyme under study to Mg2+, Ca2+-ATPase of sarcoplasmatic reticulum.
...
PMID:[SH-group and Mg2+-dependent Ca2+-activated ATPase activity of the microsome fraction of the brain]. 12 70

Mg2+-dependent Ca2+-activated ATPase (Mg2+,Ca2+-atpase, EC 3.61.4) in the fraction of synaptosome plasmatic membranes is activated with 0.05-0.08% solutions of digitonin and sodium deoxycholate. At higher concentrations of digitonin the activating effect lowers, sodium deoxycholate in the increasing concentrations inactivates the enzyme. 0.08% digitonin activates Mg2+,Ca2+-ATPase of synaptosome membranes, without demanding for its transition into solubilized state. Separation of non-active 0.08% digitonin extract from the deposit results in a decrease in the enzymatic activity of the latter and addition of the extract to the deposit activates the enzyme. At least two components separable from each other are likely to be necessary for the enzyme activity manifestation. A solubilized preparation of Mg2+,Ca2+-ATPase with the maximum activity and the ratio of total ATPase to Mg2+-ATPase equal to 3.5-4.0 may be obtained by extraction with 0.15-0.20% digitonin solution. Maximum quantily of protein is extracted by means of digitonin in the same concentrations. The extracted protein is divided in 7.5% polyacrylamide gel into eight-ten electrophoretic zones.
...
PMID:[Solubility of the Mg2+-dependant Ca2+-activated ATPase fraction of the plasma membranes of synaptosomes]. 12 71

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.
...
PMID:Absence of one component of spectrin adenosine triphosphatase in hereditary spherocytosis. 12 93


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

---