Mg2+-dependent, (Na+ + K+)-stimulated ATPase of human platelets. Properties and inhibition by ADP

J. L. Moake; K. Ahmed; N. R. Bachur; D. E. Gutfreund

doi:10.1016/0005-2736(70)90106-9

Mg²⁺-dependent, (Na⁺ + K⁺)-stimulated ATPase of human platelets. Properties and inhibition by ADP

J. L. Moake
, K. Ahmed
, N. R. Bachur
, D. E. Gutfreund

Research output: Contribution to journal › Article › peer-review

30 Scopus citations

Abstract

The preparation and properties of a Mg²⁺-dependent, (Na⁺ + K⁺)-stimulated ATPase from platelets are described. The enzym system require Mg²⁺ for activity, is stimulated maximally by the presence of Na⁺ and K⁺ in a ratio of 11.5/1, has a pH optimum 7.30-7.40, and is half-maximally inhibited by ouabain at a concentration of 0.15 μM. The K_m for ATP is approx. 0.4 mM. Enzyme activity is localized in both the "membrane" and "membrane-granule" subcellular fractions. Mg²⁺-dependent, (Na⁺ + K⁺)-stimulated ATPase activity is inhibited by ADP (which induces platelet aggregation) and by P_i. The inhibition by ADP is apparently not competitive with respect to ATP. Mg²⁺-dependent, K⁺-stimulated p-nitrophenyl phosphatase activity (a model for the externally-oriented K⁺-phosphatase portion of Mg²⁺-dependent, (Na⁺ + K⁺)-stimulated ATPase) is also inhibited by ADP. GDP, which does not induce aggregation of platelets, has no effect on the Mg²⁺-dependent, (Na⁺ + K⁺)-stimulated ATPase activity. It is postulated that ADP interacts with the external platelet membrane surface to inhibit Mg²⁺-dependent, (Na⁺ + K⁺)-stimulated ATPase activity with a resultant decrease in cation transport and membrane potential. This phenomenon may play a role in platelet aggregation.

Original language	English (US)
Pages (from-to)	337-344
Number of pages	8
Journal	BBA - Biomembranes
Volume	211
Issue number	2
DOIs	https://doi.org/10.1016/0005-2736(70)90106-9
State	Published - Aug 7 1970
Externally published	Yes

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title = "Mg2+-dependent, (Na+ + K+)-stimulated ATPase of human platelets. Properties and inhibition by ADP",

abstract = "The preparation and properties of a Mg2+-dependent, (Na+ + K+)-stimulated ATPase from platelets are described. The enzym system require Mg2+ for activity, is stimulated maximally by the presence of Na+ and K+ in a ratio of 11.5/1, has a pH optimum 7.30-7.40, and is half-maximally inhibited by ouabain at a concentration of 0.15 μM. The Km for ATP is approx. 0.4 mM. Enzyme activity is localized in both the {"}membrane{"} and {"}membrane-granule{"} subcellular fractions. Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity is inhibited by ADP (which induces platelet aggregation) and by Pi. The inhibition by ADP is apparently not competitive with respect to ATP. Mg2+-dependent, K+-stimulated p-nitrophenyl phosphatase activity (a model for the externally-oriented K+-phosphatase portion of Mg2+-dependent, (Na+ + K+)-stimulated ATPase) is also inhibited by ADP. GDP, which does not induce aggregation of platelets, has no effect on the Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity. It is postulated that ADP interacts with the external platelet membrane surface to inhibit Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity with a resultant decrease in cation transport and membrane potential. This phenomenon may play a role in platelet aggregation.",

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year = "1970",

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AU - Moake, J. L.

AU - Ahmed, K.

AU - Bachur, N. R.

AU - Gutfreund, D. E.

PY - 1970/8/7

Y1 - 1970/8/7

N2 - The preparation and properties of a Mg2+-dependent, (Na+ + K+)-stimulated ATPase from platelets are described. The enzym system require Mg2+ for activity, is stimulated maximally by the presence of Na+ and K+ in a ratio of 11.5/1, has a pH optimum 7.30-7.40, and is half-maximally inhibited by ouabain at a concentration of 0.15 μM. The Km for ATP is approx. 0.4 mM. Enzyme activity is localized in both the "membrane" and "membrane-granule" subcellular fractions. Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity is inhibited by ADP (which induces platelet aggregation) and by Pi. The inhibition by ADP is apparently not competitive with respect to ATP. Mg2+-dependent, K+-stimulated p-nitrophenyl phosphatase activity (a model for the externally-oriented K+-phosphatase portion of Mg2+-dependent, (Na+ + K+)-stimulated ATPase) is also inhibited by ADP. GDP, which does not induce aggregation of platelets, has no effect on the Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity. It is postulated that ADP interacts with the external platelet membrane surface to inhibit Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity with a resultant decrease in cation transport and membrane potential. This phenomenon may play a role in platelet aggregation.

AB - The preparation and properties of a Mg2+-dependent, (Na+ + K+)-stimulated ATPase from platelets are described. The enzym system require Mg2+ for activity, is stimulated maximally by the presence of Na+ and K+ in a ratio of 11.5/1, has a pH optimum 7.30-7.40, and is half-maximally inhibited by ouabain at a concentration of 0.15 μM. The Km for ATP is approx. 0.4 mM. Enzyme activity is localized in both the "membrane" and "membrane-granule" subcellular fractions. Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity is inhibited by ADP (which induces platelet aggregation) and by Pi. The inhibition by ADP is apparently not competitive with respect to ATP. Mg2+-dependent, K+-stimulated p-nitrophenyl phosphatase activity (a model for the externally-oriented K+-phosphatase portion of Mg2+-dependent, (Na+ + K+)-stimulated ATPase) is also inhibited by ADP. GDP, which does not induce aggregation of platelets, has no effect on the Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity. It is postulated that ADP interacts with the external platelet membrane surface to inhibit Mg2+-dependent, (Na+ + K+)-stimulated ATPase activity with a resultant decrease in cation transport and membrane potential. This phenomenon may play a role in platelet aggregation.

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DO - 10.1016/0005-2736(70)90106-9

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Mg²⁺-dependent, (Na⁺ + K⁺)-stimulated ATPase of human platelets. Properties and inhibition by ADP

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