The ATPase activity of purified myocardial myosin was activated by either K+ or Ca++. The addition of one in the presence of the other caused inhibition. According to Hill plot analyses the K+ saturation curves were sigmoidal (n = 2.92), while the Ca++ saturation curves were hyperbolic (n = 1.25). Ca++ saturation curves in the presence of K+ were inhibitory with sigmoidicity (n = 4.11), while K+ saturation curves in the presence of Ca++ followed the Michaelis Menten inhibition kinetics (n = 1.11). Substrate saturation curves were hyperbolic for both Ca++ and K+ systems. There was no enzymatic activity when Na+ was used as the activating metal; furthermore, Na+ inhibited in the presence of either K+ or Ca++. Both Na+ curves of inhibition followed the Michaelis Menten relationship.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - 1973|
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