DIFFERENT OXIDANT SENSITIVITIES OF THE ALPHA(1) AND ALPHA(2) ISOFORMSOF NA+ K+-ATPASE EXPRESSED IN BACULOVIRUS-INFECTED INSECT CELLS/

Inhibition of Na+/K+-ATPase by partially reduced oxygen metabolites is an early event in the course of cell injury caused by oxidative stres s. We showed before that isoforms of the enzyme obtained from differen t sources have different oxidant sensitivities. To evaluate the role o f tissue-specific impurities in this difference, cDNAs of alpha(1) and alpha(2) isoforms were expressed in Sf-9 insect cells, and the effect s of H2O2 on the resulting isolated enzymes were studied. The expresse d alpha(2) was significantly more sensitive than alpha(1) to H2O2. The se findings, together with our previous data showing different oxidant sensitivities of alpha(1) and alpha(3) in a cardiac enzyme preparatio n, indicate that differential oxidant sensitivities of Na+/K+-ATPase i soforms of various tissues are dictated by the primary sequences of al pha(1), alpha(2), and alpha(3) subunits. (C) 1995 Academic Press, Inc.