Studies on the characterization of the sodium-potassium transport adenosinetriphosphatase: XI. Comparison of kinetic properties of the purified with the impure membrane-bound enzyme from Squalus acanthias

Abstract

A variety of kinetic parameters have been compared in the membrane-bound and purified forms of the (sodium + potassium)-activated adenosinetriphosphatase (NaK ATPase) from the rectal gland of the spiny dogfish, Squalus acanthias. The kinetic parameters which have been studied have been temperature optima, pH optima, Mg-activation curves, optimum ATP/Mg ratios, K m for ATP, ouabain-inhibition curves, and Na and K-activation curves. All kinetic parameters were remarkably similar for both forms of the enzyme. This encourages us to believe that information obtained from the pure enzyme can be extrapolated to the enzyme in its native membrane environment and should throw light on the molecular mechanism of Na and K transport.