Activation of (Na++K+)-ATPase by long-chain fatty acids and fatty acyl coenzymes A.

Long-chain unsaturated fatty acids and fatty acyl CoA derivatives activated (Na++K+)-ATPase at suboptimal, but not optimal, ATP concentrations. Activation was obtained within a narrow range of fatty acid concentrations; higher acid levels inhibited the enzyme. The various CoA esters, however, activated with K0.5 values in the range of 0.15-10 microM; and with no inhibitory effects at concentrations up to 100 microM. Palmitoyl CoA, binding reversibly to a regulatory site, reduced K0.5 of ATP from 0.37 mM to 0.17 mM; and changed the Hill coefficient of the substrate-velocity curve from 0.86 to 0.63. These compounds may be physiological regulators that desensitize the function of this enzyme to diminishing ATP levels.