Effect of trinitrophenylation on myosin ATPase

1. The enzymic and actin binding properties of myosins trinitrophenylated to different extents in the presence or absence of ATP have been studied.

2. The enzymic properties of myosin trinitrophenylated in the absence of ATP are different from those of myosin treated in the presence of ATP even on trinitrophenylating an equal number of lysyl residues. On trinitrophenylation in the absence of ATP the EDTA-(K⁺-)activated ATPase and Ca²⁺-activated ATPase decrease while the Mg²⁺-activated ATPase considerably increases. In the presence of ATP the enzymic properties of myosin are much less affected by trinitrophenylation.

3. The actin binding capacity of trinitrophenylated myosin does not change, although its enzymic properties may be greatly altered, and even if its property to be activated by actin is completely lost.