title: Improvement of a direct spectrophotometric assay for routine determination of superoxide dismutase activity.
abstract: The growing interest in measuring superoxide dismutase (EC 1.15.1.1) in many diseases calls for useful routine assays. For this purpose, the direct spectrophotometric method of Marklund (J Biol Chem 1976;251:7504-7) was improved to offer an alternative to the imprecise, indirect assays currently used. The decay of O2.- (from KO2) at pH 9.5 was monitored as the decrease in delta A (delta A = A250nm-A360nm). Superoxide dismutase was determined from the pseudo-first-order rate constant of O2.- dismutation. The precision of the assay was improved by increasing the concentration of O2.- and expanding the interval for measurements of O2.- concentrations to 4-16 mumol/L. Other assay characteristics, including temperature, were also optimized. In hemolysate the assay had a within-day CV of 5.5-13% and a between-day CV of 4%. Mn-superoxide dismutase and some superoxide dismutase mimics are inhibited at alkaline pH. Therefore, the method is primarily recommended for Cu,Zn-superoxide dismutase.
authors.affiliation: Laboratory of Clinical Biochemistry, University of Bergen, Haukeland Hospital, Norway.
authors.forename: B J
authors.initials: BJ
authors.lastname: Bolann
authors.forename: R J
authors.initials: RJ
authors.lastname: Ulvik
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D051381:Rats; D013053:Spectrophotometry / Q000379:methods* / Q000706:statistics & numerical data; D013482:Superoxide Dismutase / Q000032:analysis* / Q000097:blood / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D013696:Temperature
chemical_list: D013481:Superoxides; D002374:Catalase; D013482:Superoxide Dismutase