Partial purification and kinetic studies of mammalian tyrosinase

1. 1. The soluble tyrosinase used in this investigation was prepared from Harding-Passey mouse melanoma by the procedure of Brown and Ward with a slight modification. 2. 2. Electrophoretic analysis at pH 8.6 showed that this soluble tyrosinase contains two enzymically active components. 3. 3. Purification of the preparation by salting-out with (NH 4) 2SO 4 did not make possible the complete separation of these two electrophoretically different components. 4. 4. The oxidation of DOPA into DOPA-quinone, as catalyzed by tyrosinase, was inhibited by tyrosine. Kinetic studies suggest that there are on the tyrosine molecule two kinds of sites: one where DOPA is oxidized and another where tyrosine is bound but not oxidized during the first phase of the reaction.