Inhibition of (Na,K)ATPase by the extract from Artemia salina

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Measurement of levels of (Na,K) ATPase subunit in developing Artemia salinahas indicated that both alpha and beta subunit are present in the embryos of this organism in the early stage of development. Nevertheless, Artemia in these stages does not show any detectable (Na,K)ATPase activity, suggesting that the presence of inhibitors for (Na,K)ATPase in developing Artemia. In this study, the endogenous inhibitors were isolated from Artemia and characterized as follows;1. Digestion of the inhibitors with trypsin or papain did not have any significant effect of their inhibitory activity. Furthermore heat treatment did not affect the inhibitory activity.2. The inhibitors extracted with organic solvent yielded two active spots on TLC plates, both containing longchain fatty acids. These results suggested that the inhibitory activity found in Artemia were due to non-esterified long chain fatty acids and their esters. In order to examine the effect of fatty acids on (Na,K)ATPase, the enzyme was purified from Artemia and delipidated with a detergent, CHAPS.3. Upon delipidation, the activity was although 10-25 phospholipids were still left on an enzyme.4. With the addition of exogeneous phospholipids, the activity was restored. The enzyme delipidated in the presence of KCl reassociated phospholipids more firmly than the enzyme delipidated in the presence of NaCl.The delipidated enzyme would be a good tool for studying the action of fatty acids on (Na,K)ATPase