Tyrosinase and phenolic pressor amines

Basic to the consideration of the action of tyrosinase on the oxidation of phenolic pressor amines are the observations of Keilin and Mann (16) and of Nelson and his coworkers (17-19) that show that different preparations may vary considerably in their relative actions on monophenols and o-diphenols. Both of these types of activity appear to belong to the same enzyme complex, as they bear a proportionality to the same copper content. However, since the activities vary with the purity and method of purification, each enzyme preparation must be defined in terms of both monophenolase and o-diphenolase activities. This was done in the present studies, and modifications of previously described preparative methods were required to retain a reasonable proportioning of such activities in purified preparations.