[Effect of phospholipase A2 from Naja naja oxiana venom on activity of Na+,K+-ATPase isoenzymes in rat brain].

The specific sensitivity of the isoforms of the rat brain Na+,K(+)-ATPase catalytic subunit to phospholipase A2 (PL A2) from Naja naja oxiana venom has been estimated on the basis of changes in the two-component dose response curve of ouabain inhibition of Na+,K(+)-ATPase activity. Moderate Na+,K(+)-ATPase inactivation of PL A2 is accompanied by a decrease of the apparent affinity for ouabain in comparison with the untreated enzyme without any significant changes in the isoform activity ratio in the preparation. This effect is eliminated by washing of the preparation with serum albumin and seems to be mediated by the effect of free fatty acids on the enzyme. At a high level of Na+,K(+)-ATPase inactivation, the alpha-isoforms is inactivated more rapidly than the alpha (+)-isoform.