| Abstract
| - Recombinant thioredoxin h (Trx2) overproduced in Escherichia coli (M15) was purified by Ni2+-chelatedaffinity chromatography. The molecular mass of Trx2 is ∼1.4 kDa as determined by sodium dodecylsulfate−polyacrylamide gel electrophoresis. Total antioxidant status, 1,1-diphenyl-2-picrylhydrazyl(DPPH) staining, reducing power method, Fe2+-chelating ability, ferric thiocyanate (FTC) method,and protection of calf thymus DNA against hydroxyl radical-induced damage were studied. Thethioredoxin h protein with a concentration of 12.5 mg/mL exhibited the highest activity (expressed as0.37 ± 0.012 mM ABTS• radical cation being cleared) in a total antioxidant status test. In the DPPHstaining thioredoxin h appeared as white spots when it was diluted to 50 mg/mL (a final amount of15 μg). Like the total antioxidant status, the reducing power, Fe2+-chelating ability, FTC activity, andprotection against hydroxyl radical-induced calf thymus DNA damage were found with the thioredoxinh protein. It was suggested that thioredoxin h might contribute to its antioxidant activities againsthydroxyl and peroxyl radicals. Keywords: Sweet potato; thioredoxin h; cDNA sequence; gene expression; recombinant protein;antioxidant
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