The Active Site of Myosin Adenosine Triphosphatase

The active site of myosin adenosine triphosphatase. I. Localization of one of the sulfhydryl groups.

It is now widely recognized that under certain conditions of temperature and pH (1, 2)) the Ca++-activated hydrolysis of adenosine triphosphate (ATP) by myosin exhibits a biphasic response to titration of the sulfhydryl groups of the protein by organic mercurials and by N-ethylmaleimide (3-5). On the other hand, titration by these reagents results only in inhibition if inosine triphosphate or g...

Adrenergic regulation of myosin adenosine triphosphatase activity.

The amount of inorganic phosphate liberated by the adenosine triphosphatase activity of myosin in a thin section of cardiac tissue can be measured quantitatively by precipitation with calcium in an alkaline medium under a defined set of conditions. Specificity of the procedure for myosin adenosine triphosphatase has been confirmed by the response to inhibitors and to different degrees of contra...

Hormonal control of cardiac myosin adenosine triphosphatase in the rat.

Cardiac function was impaired in hearts from hypophysectomized rats. Corresponding to the decrease in performance, myosin from the hearts of these rats exhibited a decreased Ca -activated ATPase activity. Myosin ATPase activated by K or NH4 + was not different in any of the preparations studied. The decreased Ca -activated ATPase was observed in cardiac myosin but not in red or white skeletal m...

Reversible denaturation in the myosin adenosine triphosphatase system.

Stimulation of cardiac myosin adenosine triphosphatase in thyrotoxicosis.

THE striking cardiovascular manifestations of thyrotoxicosis have attracted the interest of clinicians and researchers for many years. Caleb H. Parry (1785) probably was the first to note an association between enlargement of the thyroid and enlargement or palpitations of the heart. It is now known that excess thyroid hormone, either produced endogenously or administered exogenously, produces h...