Inhibitory effect of melittin on Na~+ , K~+ -ATPase from guinea pig myocardial mitochondria

Aim: To investigate the effect of melittin (Mel) of Na+,K+-ATPase activity and it's kinetic mode of action on guinea pig myocardial mitochondria. Methods: Effect of Mel on heart mitochondrial Na+,K+-ATPase activity was determined with colorimetry method. Results: Mel inhibited Na+,K+-ATPase in a concentration and time dependent manner, IC50 was 2.60 micromol/L. Kinetic studies of interaction between Mel and K+, Na+, ATP revealed that inhibitory effect of Mel was competitive with K+, but not with Na+ and ATP. Conclusion: Mel polypeptide potently inhibits Na+,K+-ATPase, possibly by binding to the K+ site.