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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)

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.
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PMID:[SH-group and Mg2+-dependent Ca2+-activated ATPase activity of the microsome fraction of the brain]. 12 70

The adenylate cyclase activity from a rat liver plasma membrane preparation was inhibited by low concentrations (1-10 muM) of the mercurial diuretic mersalyl. Complete inhibition was obtained with 0.1 mM mersalyl. Similar effects were observed whether the adenylate cyclase preparation was assayed in the presence of 10 muM GTP, 0.1 muM glucagon, 10 mM NaF or without any addition. The effect of mersalyl was not due to inhibition of the regenerating system present in the incubation medium, since the effect of mersalyl was preserved and even enhanced in its absence. The inhibition brought about by mersalyl was due to both a decrease of the maximal velocity of the reaction and of the affinity of the enzyme for the substrate. It was immediate, and irreversible spontaneously, but it was reversed by the simultaneous additions of 2-mercaptoethanol, in a dose-dependent fashion. Other -SH reagents were found to have an effect equal to, or lower than, that of mersalyl. Mersalyl had no effect upon Mg2+-ATPase, although it inhibited the (Na+-K+) activated ATPase. Since mersalyl is known to be a 'non-penetrant' reagent, it is postulated that a catalytically important, mercurial-sensitive, part of adenylate cyclase is at the surface of the plasma membrane. This view is supported by the following facts: (a) mersalyl acted with a similar dose-response curve upon an intact as well as a detergent-dispersed cyclase preparation while no effect was observed upon a solubilized Mg2+-ATPase preparation; (b) a covalent p-chloromercuribenzoate-Sephadex preparation (but not its supernatant) inhibited the cyclase from intact membranes. It is proposed that mercurial derivatives, by their relative specificity of action (no effect on Mg2+-ATPase), can serve as useful probes in the elucidation of the multicomponent structure of the cyclase system.
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PMID:Adenylate cyclase from rat-liver plasma membrane: inhibition by mersalyl and other mercurial derivatives. 12 56

Interaction of adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S) with Ca2+,Mg2+-ATPase of sarcoplasmic reticulum was studied. The nucleotide was slowly hydrolyzed by the ATPase at 30 degrees C at a rate of about 0.5% that of ATP hydrolysis. Whereas at 0 degrees C, ATP gamma S showed only a limited reactivity toward the ATPase in that a thiophosphorylated intermediate was formed and ADP was released, but hydrolysis of the intermediate to complete the catalytic cycle did not occur. A fairly stable analog of the E-P intermediate could thus be obtained. Presence of the thiophosphorylated intermediate was indicated by the [3H]ADP in equilibrium ATP gamma S exchange reaction and also by using [35S]ATP gamma S. When the ATPase was reacted with ATP gamma S at 0 degrees C in the presence of ferricyanide, EP-forming activity was rapidly lost. Free Ca2+ ions were required for this inactivation. Disulfide bond formation between a cysteinyl residue located near the substrate binding site and the enzyme-bound ATP gamma S or the thiophosphorylated intermediate was suggested by the fact that 2-mercaptoethanol reversed the inactivation. The reaction may prove to be a useful tool for affinity labeling of the active site of the ATPase.
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PMID:Interaction of adenosine-5'-O-(3-thiotriphosphate) with Ca2+,Mg2+-adenosine triphosphatase of sarcoplasmic reticulum. 612 38

The ATP-dependent proton pump which was previously identified in clathrin-coated vesicles isolated from calf brain (Forgac, M., Cantley, L., Wiedenmann, B., Altstiel, L., and Branton, D. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 1300-1303) is further characterized. 7-Chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl) was identified as a potent inhibitor of both ATP-dependent proton uptake and Mg2+-ATPase activity of coated vesicles. Thus, incubation with 10 microM NBD-Cl for 10 min at 23 degrees caused the loss of 80% of the Mg2+-ATPase activity and 95% of the proton pumping activity. The observed protection from NBD-Cl inhibition by ATP suggests that NBD-Cl may react at the catalytic site, and reversal of NBD-Cl inhibition by 2-mercaptoethanol is consistent with reaction at either a tyrosine or cysteine residue. In addition, no stable phosphorylated intermediate was observed during turnover of the coated vesicle proton pump and neither Na+ nor K+ was countertransported by the pump during ATP-dependent proton uptake.
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PMID:Characterization of the ATP-dependent proton pump of clathrin-coated vesicles. 614 11