Detection of superoxide dismutase (Cu-Zn) isoenzymes in leaves and pseudobulbs of Kraenzl orchid by comparative proteomic analysis.

Typically, biological systems are protected from the toxic effect of free radicals by antioxidant defense. Extracts from orchids have been reported to show high levels of exogenous antioxidant activity including orchids but so far, there have been no reports on antioxidant enzymes. Therefore, differences in protein expression from leaves and pseudobulbs of Kraenzl and Earsakul were studied using two-dimensional gel electrophoresis and mass spectrometry (LC/MS/MS). Interestingly, the largest group of these stress response proteins were associated with antioxidant defense and temperature stress, including superoxide dismutase (Cu-Zn) and heat shock protein 70. The high expression of this antioxidant enzyme from Kraenzl was confirmed by activity staining on native-PAGE, and the two Cu/Zn-SODs isoenzymes were identified as Cu/Zn-SOD 1 and Cu/Zn-SOD 2 by LC/MS/MS. The results suggested that orchid can be a potential plant source for medicines and natural antioxidant supplements.