The Ukrainian Biochemical Journal
Journal archive > 2015 > N 1 January-February
A. A. Kaplia
To elucidate the specific features of the АТР- hydrolases structural resistance in the membrane under the action of the prooxidants: Fe2+ and hydrogen peroxide, and N-ethylmaleimide (NEM) the colonic smooth muscle (CSM) Na+,K+-AТРase activity was compared with activities of the corresponding Mg2+-АТР-hydrolase and ATP-ases from kidney medullar layer of rats. The inhibition study of the CSM Na+,K+-AТРase by divalent iron shows the decrease of the activity by 30% at 0.1 µM FeSO4 and in the range of 0.1-10 µM – to 45% of residual activity. When comparing with kidney enzyme (represents exclusively α1-isozyme) the CSM Na+,K+-AТРase sensitivity to Fe2+ is reliably higher at its submicromolar concentration. CSM Mg2+-АТРase is much more resistant to iron ions effect, than kidney one. However for two tissues Mg2+-АТРase activity is always more resistant as compared with corresponding Na+,K+-AТРase activity. Against 1 mM EGTA Na+,K+-AТРase and Mg2+-АТРase activities of GMOK and kidneys are equally insensitive to effect of hydrogen peroxide in concentration up to 1 mM. But in the presence of 20 µM FeSO4 in the concentration range of 1 nМ – 1 mM of Н2О2 the Na+,K+-AТРase is inhibited to greater extent, than Mg2+-АТРase activity. NEM sensitivity of the two АТР-hydrolase systems corresponds to prooxidant sensitivity that indicates the distinct importance of SH-groups for their functioning. It is concluded that Na+,K+-AТРase can serve as a marker of membrane sensitivity to oxidation, Mg2+-АТРase is resistant to oxidation and can be considered as criterion of the oxidation resistance when comparing membrane enzyme complexes, especially in GMOK.
Key words: ATP-hydrolases, Na+,K+-AТРase, colonic smooth muscle, kidney, prooxidants, ferrum ions, hydrogen peroxide, N-ethylmaleimide.
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