Cell membrane Ca2+/Mg2+ ATPase

Dhalla, Naranjan S.; Zhao, Dayuan

doi:10.1016/0079-6107(88)90006-5

Cited by 57 publications

(21 citation statements)

References 229 publications

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“…Since ATP-independent Ca2+-binding in heart sarcolemma is considered to represent the superficial store of Ca 2+ which is available for Ca 2+ influx upon excitation of the myocardial cell (10), it is likely that this site may contribute towards changes in Ca 2+ movements across the cell upon exposure to oxygen free radicals. This mechanism would be complimentary to the sarcolemmal Ca2+fMg 2+ ATPase, which is considered to serve as a Ca2+-gating system for the entry of Ca e+ into the myocardial cell (8,10,11) since similar alterations in ATP-independent binding and Ca2+/Mg2+ ATPase due to oxygen free radicals were observed in this study. Changes in Ca 2+ movements in the cardiac cell due to oxygen free radicals have also been suggested to occur due to abnormalities in the sarcolemmal Ca2+-pump, Na+-K + ATPase and Na+-Ca 2+ exchange systems as well as the sarcoplasmic reticular CaZ+-pump mechanism (16,17,28,29).…”

Section: Discussionmentioning

confidence: 85%

“…Although oxygen free radicals are also known to react with SH-groups in the membrane proteins (12,29), it is unlikely that the observed changes in the sarcolemmal Ca2+/Mg 2+ ATPase arc due to oxidation of SH-groups in the enzyme complex. In this regard, different SH-groups inhibitions were found to exert no effect on the membrane bound Ca2+/Mg 2+ ATPase (11).…”

Section: Discussionmentioning

confidence: 96%

“…Heart sarcolemmal membrane has been shown to contain an ATPase system which is activated by millimolar concentrations of divalent cations such as Ca 2+ or Mg 2+ (1,8,11). Treatment of the heavy sarcolemmal fraction with trypsin was found to release a component of the ATPase system which is primarily activated by Ca 2+ (Ca2+-dependcnt ATPase) whereas the remaining part of the enzyme complex was stimulated by Ca 2+ or Mg 2+ (Ca2+/ Mg 2+ ATPasc) (7).…”

Section: Discussionmentioning

confidence: 97%

“…Although the exact mechanisms for the altered Ca2+/Mg 2+ ATPase activities in heart sarcolemma from different discased hearts are not clear, it is possible that such changes at any given stage and type of heart disease may depend upon the local concentration as well as the source of oxygen free radicals. Since oxygen free radicals are known to promote the peroxidation of membrane phospholipids (12), and since changes in membrane phospholipids have been shown to be associated with alterations in the sarcolemmal Ca2+/Mg 2+ ATPase activities (11), it is likely that the changes in the sarcolemmal Ca2+-ATPase and Mg2+-ATPase are due to alterations in the phospholipid composition of the membrane. Although oxygen free radicals are also known to react with SH-groups in the membrane proteins (12,29), it is unlikely that the observed changes in the sarcolemmal Ca2+/Mg 2+ ATPase arc due to oxidation of SH-groups in the enzyme complex.…”

Section: Discussionmentioning

confidence: 99%

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Alterations in heart sarcolemmal Ca2+-ATPase and Ca2+-binding activities due to oxygen free radicals

1990

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Effects of oxygen free radicals on Ca2+/Mg2+ ATPase and ATP-independent Ca2(+)-binding activities were examined in rat heart sarcolemma. Membranes were incubated with different oxygen radical generating media such as xanthine + xanthine oxidase, hydrogen peroxide, and hydrogen peroxide + Fe2+. In the presence of xanthine + xanthine oxidase, Ca2+ ATPase activity was stimulated and this effect was prevented by the addition of superoxide dismutase. Hydrogen peroxide also showed a significant increase in Ca2(+)-ATPase activity in a dose-dependent manner and this effect was blocked by catalase. On the other hand, a combination of hydrogen peroxide + Fe2+ decreased Ca2(+)-ATPase activity; this depression was prevented by the addition of D-mannitol. The observed change in Ca2(+)-ATPase activity due to oxygen free radicals was associated with changes in Vmax, whereas Ka remained unaffected. Both xanthine + xanthine oxidase and hydrogen peroxide increased whereas, hydrogen peroxide + Fe2+ inhibited the ATP-independent Ca2(+)-binding activities. It is suggested that oxygen free radicals may influence Ca2+ movements in the cell by altering the Ca2+/Mg2+ ATPase and Ca2(+)-binding activities of the membrane and these effects may be oxygen-radical species specific.

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Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Alterations in heart sarcolemmal Ca2+-ATPase and Ca2+-binding activities due to oxygen free radicals

1990

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“…It has been proposed that, in addition to the substrate catalytic site, another binding site exists for the substrate and that conformational changes are related to the occupancy of this putative regulatory (inhibitory) site [5]. In this regard, purified rat heart Mg# + -ATPase was found to bind adenosine 5h-[γ-[$&S]thio]triphosphate with two affinities [32] ; several ecto-ATPases, including that of chicken muscle, use MgATP# V as substrate with two apparent K m values for the high-affinity (10-100 µM) and low-affinity (0.2-8 mM) ATP-binding sites ( [8,33], and this study). In the chicken T-tubule ecto-ATPase, Con A and glutaraldehyde exerted no effect if added after ATP ( Table 2), suggesting that when the regulatory site is occupied the enzyme loses its ability to respond to these compounds and that it remains in the lowactivity state, although it can be assumed that cross-linking of the membrane components would not be avoided by such a small molecule as ATP.…”

Section: Scheme 1 Proposed Model For the Regulation Of Chicken T-tubumentioning

confidence: 99%

Regulation of transverse tubule ecto-ATPase activity in chicken skeletal muscle

Megías

Martinez-Senac

Delgado

et al. 2001

Biochemical Journal

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Transverse tubule (T-tubule) ecto-ATPase from chicken skeletal muscle is an integral membrane glycoprotein that seems to exist as a homodimer and exhibits unusual properties. Treatment of T-tubule membranes with concanavalin A (Con A) did not significantly affect the thermal variation of the fluorescence anisotropy of vesicles labelled with 1,6-diphenyl-1,3,5-hexatriene or trimethylammonium-1,6-diphenyl-1,3,5-hexatriene. Cross-linking of membrane components with glutaraldehyde elicited effects on ecto-ATPase activity very similar to those of Con A treatment: a severalfold increase in activity, a decrease in Triton X-100 sensitivity and a requirement to be present before ATP to exert its action. In addition, glutaraldehyde and Con A normalized the temperature dependence and the kinetic behaviour of the enzyme. Membrane-perturbing agents (detergents, alcohols and cholesterol oxidase), with the sole exception of digitonin, caused a marked decrease in ecto-ATPase activity; the prior presence of Con A prevented this inhibition, whereas when the lectin was added after the membrane perturbing agent, recovery of the activity was not always possible. The addition of nucleotides before Con A led to a suppression of ecto-ATPase stimulation; it occurred when the nucleotide was hydrolysed (ATP or UTP) and when it was not (adenosine 5′-[β,γ-imido]triphosphate) and even in the presence of 3mM Pi. A model is proposed for the complex regulatory mechanisms of chicken T-tubule ecto-ATPase that involves the occurrence of two different catalytic states in an equilibrium modulated by lectins and cross-linking agents, by the structure of the membrane and by the presence of ligands for a regulatory site.

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