Activatory action of trypsin on epidermis dopa-oxidase.

Trypsin activated the Dopa-oxidase enzyme of frog epidermis, while carboxypeptidase "a" achieved only 50% of this activation. The enzyme can be activated by passing it through a column of insoluble trypsin coupled to Sepharose. Some properties of inactive and active dopa-oxidase are compared: a) Apparent molecular weight and Stokes radius of active enzyme are higher than those of the inactive one. b) The entropy change for denaturation of inactive enzyme is about 108 cal times mol-1 times degrees K-1; while the value is only --3.6 cal times mol-1 times degrees K-1 for the active enzyme. It is hypothesized that the activatory process consists of a tryptic rupture accompanied by a spatial unfolding of the enzyme molecule.