Effect of 2,3−Butanedione Monoxime on Myosin and Myofibrillar ATPases. An Example of an Uncompetitive Inhibitor

2,3−Butanedione monoxime (BDM) reversibly inhibits force production in muscle. At least part of its action appears to be directly on the contractile apparatus. To understand better its mechanism of action, we studied the effect of BDM on the steps of myosin subfragment 1 MgZ+−ATPase in 0.1 M potassium acetate, pH 7.4. Because of the rapidity of certain processes, we experimented at 4 OC and our main technique was the rapid flow quench method. By varying the experimental conditions (relative concentrations of reagents, time scale, quenching agent), it was possible to study selectively the different steps of the S1 MgZ+−ATPa