Demonstration of dopa oxidase activity by purified mammalian superoxide dismutase using polyacrylamide gel electrophoretic separation

Abstract

Purified bovine erythrocyte superoxide dismutase (SOD) was separated by polyacrylamide gel electrophoresis. Gels which were stained for protein showed a single major band (Rx-0.41). Gels which were stained for SOD activity showed a single achromatic band (Rx-0.41) and gels which were stained for dopa oxidase activity also showed a single grey-black band (Rx-0.41). Rx values of other oxidases (horseradish peroxidase, mushroom tyrosinase, catalase and melanoma “tyrosinase” (L-dopa Oxidase) were significantly different from that of SOD. The dopa oxidase activity of SOD may be important as an alternative pathway for melanin synthesis with resultant free radical quenching by melanin and its intermediates. This secondary function is in addition to its primary function as a superoxide dismutase. These functions may be interrelated in some circumstances when L-dopa acts as the proton donor of the dismutase reaction: .