Difference in phospholipid dependence between two isozymes of brain (Na+ + K+)-ATPase.
The effect of phospholipase C on two isozymes (alpha (+) and alpha forms) of rat brain (Na+ + K+)-ATPase and the temperature-dependence of their activities were investigated. Phospholipase C from Clostridium welchii inhibited the activities of the enzymes treated with and without pyrithiamin or N-ethylmaleimide, a preferential inhibitor of the alpha (+) form, but the extent of the inhibition was higher in the control enzyme than in the treated enzymes. The treatment of the (Na+ + K+)-ATPase with phospholipase C altered a ratio between high- and low-affinity components for ouabain inhibition. It also caused the similar change in a ratio between the alpha (+) and alpha forms of Na+-stimulated phosphorylation from [gamma-32P]ATP. These findings indicate that the alpha (+) form of rat brain (Na+ + K+)-ATPase is more sensitive to phospholipase C than the alpha form. Analysis of Arrhenius plots of the activities of the control and pyrithiamin-treated enzymes showed that there was a difference between the two enzymes in a break point. We suggest that two isozymes of rat brain (Na+ + K+)-ATPase differ in the interaction with phospholipids or in the lipid-environment.
D000818:Animals; D002540:Cerebral Cortex / Q000201:enzymology*; D005033:Ethylmaleimide / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D010743:Phospholipids / Q000378:metabolism*; D011745:Pyrithiamine / Q000494:pharmacology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013108:Sphingomyelin Phosphodiesterase / Q000494:pharmacology; D013696:Temperature; D010738:Type C Phospholipases / Q000378:metabolism
D007527:Isoenzymes; D010743:Phospholipids; D010042:Ouabain; D011745:Pyrithiamine; D010738:Type C Phospholipases; D013108:Sphingomyelin Phosphodiesterase; D000254:Sodium-Potassium-Exchanging ATPase; D005033:Ethylmaleimide