The smooth adductor myosin of the scallop Patinopecten yessoensis was examined on its physico-chemical and enzymatic properties. It was found to have a sedimentation constant (S⁰_{20, W}) of 6.65 S, a molecular weight of about 450, 000, and an intrinsic viscosity of 1.76 dl/g. It is completely soluble in 0.25_M KCl and salts out with ammonium sulfate between 34-40% saturation. It exhibits an absorption maximum at 277 nm with E^1%_1cm 5.2. In amino acid composition, it is rich in Glu and Asp and poor in several amino acids such as His and Trp.
In the presence of 0.5_M KCI, it exhibits two pH optima at around 7 and 9 for Ca²⁺- ATPase activity. The optimum KCl concentration for ATPase activity is 0.2_M at pH 7.5. The activation effect of EDTA is insignificant.
Thus, the smooth adductor myosin of scallop closely resembles myosins from various sources in physico-chemical properties. In enzymatic properties, however, it differs somewhat from other invertebrate myosins.