title: Cyanide insensitive iron superoxide dismutase in Euglena gracilis. Comparison of the reliabilities of different test systems for superoxide dismutases.
abstract: Two proteins (P1 and P2, with weights of 57,500 and 27,500 respectively) were isolated from Euglena gracilis. Both proteins show cyanide-insensitive superoxide dismutase activity in the "classical" superoxide dismutase assay, using xanthine-xanthine oxidase as O2.- generator. If O2.- is generated chemically (autoxidation of reduced anthraquinone), photochemically (illuminated riboflavine) or pulse radiolytically, only protein P1 but not P2 shows SOD activity. Protein P1 contains 1 g atom (determined: 0.82) iron (no Mn or Cu) per mole protein and may thus be defined as iron-superoxide dismutase. Protein P2, showing the spectral properties of a flavoprotein, exhibits the activities of ferredoxin-NADP-oxidoreductase and "diaphorase". The cyanide-insensitive SOD-activity of this Diaphorase" in the xanthine oxidase-assay for superoxide dismutase makes this classical and commonly used test unreliable for assay cyanide insensitive SOD activities. The existence of the "prokaryote-type" of superoxide dismutase (Fe-SOD) in Euglena gracilis is exceptional for an eukaryotic, autotrophically grown organisms.
mesh_terms: D015086:2,6-Dichloroindophenol; D000818:Animals; D003486:Cyanides / Q000494:pharmacology*; D005055:Euglena / Q000201:enzymology*; D005288:Ferredoxins; D007700:Kinetics; D008970:Molecular Weight; D009243:NAD; D010101:Oxygen Consumption; D013379:Substrate Specificity; D013482:Superoxide Dismutase / Q000032:analysis / Q000378:metabolism*
chemical_list: D003486:Cyanides; D005288:Ferredoxins; D009243:NAD; D015086:2,6-Dichloroindophenol; D013482:Superoxide Dismutase