Reaction of myosin with salicylaldehyde II. Effect of salicylalation on the ATPase activity of myosin

The effect of salicylalation on the biological properties of myosin was studied. 1. 1. The ATPase activity of myosin is affected by salicylalation if the treatment is carried out at higher pH than 6.5. The Mg²⁺-activated ATPase shows a maximal curve with 250-380% maximal activation when 25-70 moles of salicylaldehyde are bound per mole of myosin. The EDTA-activated ATPase decreases with increasing salicylalation. Ca²⁺-activated ATPase shows a small increase with increasing salicylalation. 2. 2. Less salicylaldehyde is bound if the treatment is carried out in the presence of ATP, while that of PP_i does not affect the degree of salicylalation. The enzymic properties of myosins salicylalated in the presence of ATP or PP_i are not different from those of the samples treated in their absence. 3. 3. Salicylalation decreases ATP sensitivity of ATPase and superprecipitation of actomyosins reconstituted from salicylalated myosins only if more than 50 moles of salicylaldehyde are bound per mole myosin.