Characterization of superoxide dismutase from mammalian skin epidermis.

Superoxide dismutase provides a protective defense mechanism in cellular compartments against the potential cytotoxicity of superoxide anion generated by ultraviolet radiation. Little information is available about the nature of superoxide dismutase in mammalian skin. We report the isolation and characterization of superoxide dismutase from human, guinea pig, and mouse epidermis. Copper-zinc superoxide dismutase was detected in all the mammalian skin specimens examined. Manganese superoxide dismutase was detected in human and guinea pig epidermis but not in the newborn or adult albino CD1 mouse epidermis. Electrophoresis studies of the extracted and partially purified skin superoxide dismutase on polyacrylamide gel slabs in the presence of sodium dodecylsulfate showed the characteristic molecular weights for subunits of 16,500 for copper-zinc superoxide dismutase, and 23,500 for mangano superoxide dismutase. Studies under nondenaturing conditions revealed significant differences in the mobility of the enzymes, depending on the sources of superoxide dismutase. The mouse epidermal copper-zinc superoxide dismutase was found similar to the bovine liver copper-zinc superoxide dismutase used as an internal standard. The copper-zinc superoxide dismutase of human skin and guinea pig skin showed activity-stained bands characterized by a higher mobility than the same enzyme from mouse or bovine liver. Quantitative data using the beta-NADH oxidation method indicated a 5-10-fold lower content of superoxide dismutase in mammalian epidermis in comparison with other tissues examined during this study, or compared with reported values in the literature.