Vanadate sensitivity of NA +, K +-ATPase from [formula omitted] and its modulation by Na +, K + and Mg 2+

Abstract

Vandate inhibitory effects on Na +, K +-ATPases from carsas of Schistosoma mansoni and from lamb kidney outer medulla were compared in the presence of various concentrations of Na +, K + and Mg 2+. Depending on the ionic conditions, the schistosomal Na +, K +-ATPase was 2.4 -to 175-fold less sensitive to vanadate than the lamb kidney enzyme. In 100 mM Na +, 3 mM K + and 3 mM Mg 2+, schistosomal Na +, K +-ATPase was surprisingly resistant to vanadate ( I 50 = 944 μM). The difference in vanadate sensitivity between schistosomal and lamb Na +, K +-ATPases may be due to a species difference in the efficacy of Na +, K + and Mg 2+ in promoting conformational changes between E 1 and E 2 forms of the enzyme.