Purified myocardial myosin ATPase activity is activated by K+ or Ca++ but inhibited when both are present or when Na+ is added, suggesting complex allosteric regulation by physiological ions.
May modulate cardiac contractility via ion allostery; leaves open in vivo relevance and human therapeutic translation.
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.
No takes yet. Share an insight, caveat, or question.
Fenner et al. (1973) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: