Determination of manganese superoxide dismutase activity by direct spectrophotometry

• Published in: Free radical research Vol. 25; no. 6; p. 541
• Main Authors: Bolann, B J, Tangerås, A, Ulvik, R J
• Format: Journal Article
• Language: English
• Published: England 01-01-1996
• Subjects: Animals; Catalysis; Cattle; Mitochondria, Liver - enzymology; Oxygen - metabolism; Rats; Spectrophotometry; Superoxide Dismutase - metabolism
• ISSN: 1071-5762
• DOI: 10.3109/10715769609149075

A method to determine Mn-superoxide dismutase activity by measuring directly the rate of decay of O2- in a spectrophotometer, is described. Decay of O2- generated by KO2 at pH 9.5, was monitored as the fall in absorbance (A250nm-A360nm). Mn-superoxide dismutase was determined as the activity of cyanide-resistant superoxide dismutase, calculated from the rate of O2- dismutation. Mn-superoxide dismutase could be determined in the presence of a 700 times higher Cu,Zn-superoxide dismutase activity. The alkaline pH did not cause analytical problems. The assay was used to measure both Mn- and Cu,Zn-superoxide dismutase activity in mitochondrial preparations. The assay had a detection limit of 2.8 ng/ml when Mn-superoxide dismutase from E. coli was used, and the between-day CV was 5.8%. The assay is an alternative to indirect methods for detecting superoxide dismutase activity.