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Characterization of an iron‐containing superoxide dismutase from a higher plant, Citrus limonum
Author(s) -
Almansa Maria S.,
Rio Luis A.,
Sevilla Francisca
Publication year - 1994
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1994.tb00397.x
Subject(s) - superoxide dismutase , chemistry , enzyme , biochemistry , hydrogen peroxide , peroxidase
An iron‐containing superoxide dismutase (SOD, EC 1.15.1.1) was fully characterized from leaves of the higher plant Citrus limonum R. cv. Verna. This enzyme is the first iron‐containing SOD to be characterized in the plant family Rutaceae . The purified Fe‐SOD has a molecular mass of about 47 kDa and is composed of two non‐covalently joined equal subunits. The amino acid composition determined for the enzyme was compared with that of a wide range of SODs and had highest degree of homology with the Fe‐SODs from Brassica campestris and Nuphar luteum . The enzyme was more labile at high temperatures than some eucaryotic and procaryotic Fe‐SODs. It showed a maximum stability at pH 7.8. The sensitivity of the enzyme to cyanide, hydrogen peroxide and o ‐phenanthroline was similar to those reported for other Fe‐SODs. but the lemon enzyme was comparatively resistant to H 2 O 2 . By kinetic competition experiments, the rate constant for the disproportionation of superoxide radicals by lemon Fe‐SOD was found to be 1.9 × 10 9 M −1 s −1 at pH 7.8 and 25°C. A comparative study between the molecular properties of this higher plant Fe‐SOD and SODs from different origins is presented.