Studies on Proteolysis in Stored Muscle

Part IV. Effect of Cathepsin D Treatment on ATPase Activity of “Myosin B”

Abstract

The amounts of proteolytic products derived from each fraction of rabbit muscle proteins by purified cathepsin D from rabbit muscle, and the effects of cathepsin D and pepsin treatments on ATPase activity of myosin B were studied.
Water-soluble protein was most rapidly hydrolyzed, followed by myosin A, actin, and myosin B.
In comparison with the control, the decrease of the Mg-enhanced ATPase activity of myosin B treated with cathepsin D was observed, but no difference was observed in the Ca-enhanced ATPase activity of myosin B by this treatment.
The removal of native tropomyosin in myosin B was not recognized by cathepsin D treatment, which was different from trypsin treatment.
The effect of pepsin treatment on the Mg-enhanced ATPase activity of myosin B was fairly similar to that of cathepsin D treatment.