Purification and partial characterization of the Cu, Zn superoxide dismutase from the dermatophyte Trichophyton mentagrophytes var interdigitale

Cell homogenization, isoelectric focusing and gel filtration FPLC have been used to purify a superoxide dismutase (SOD) from the dermatophyte Trichophyton mentagrophytes var. interdigitale (T. interdigitale), N-terminal amino acid sequencing identified this enzyme as a Cu,ZnSOD, with a pH of 5.1, a reduced molecular mass of 18 kDa, and a non-reduced molecular mass of 59 kDa. SOD activity was detectable in culture filtrates, as early as the mid-log phase of growth. The known Cu,Zn inhibitor potassium cyanide caused some inhibition of the purified enzyme, whereas the inhibitors sodium azide, guanidinium hydrochloride, EDTA and chloroform/ethanol had no discernible effect. The T. interdigitale SOD was pH insensitive in the range 7.0-10.5 and remained active after prolonged incubation at 50 degrees C. The purification and characterization of this enzyme represents the first step in determining whether SOD plays any part in protecting T. interdigitale from free radicals generated by the oxidative burst of immune effecter cells.