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KMID : 0368419990420030187
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Journal of Plant Biology
1999 Volume.42 No. 3 p.187 ~ p.193
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Changes in the Isozyme Composition of Antioxidant Enzymes in Response to Aminotriazole in Leaves of Arabidopsis thaliana
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Kang, Kyong Suk
Lim, Chang Jin/Han, Tae Jin/Kim, Joon Chul/Jin, Chang Duck
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Abstract
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The changes in isozyme profiles of catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR) during severe deactivation of total CAT activity by aminotriazole (AT) treatment were investigated in the leaves of Arabidopsis thaliana (Columbia ecotype) in relation to H_2O_2-mediated oxidative stress. In spite of striking deactivation of total CAT activity by 0.1mM AT, there were no significant differences in H_2O_2 levels or total leaf soluble protein contents including a Rubisco in both the control and AT-treated leaves. On the other hand, one specific protein band (molecular mass, 66 kD) was observed on the SDS-gel from leaf soluble proteins whose staining intensity was strikingly enhanced by AT treatment for 6 h. However, this band disappeared at 12 h. In the native-gel assays of CAT, POD, APX and GR isozymes, AT remarkably inhibited the expression of the CAT1 isozyme with no effects on CAT2 and CAT3, and generally had no effect on POD isozyme profiles. However, AT stimulated the intensity of activities of pre-existing APX1 and GR1 isozymes. In particular, it induced a new synthesis of one GR isozyme. Therefore, these results collectively suggest that a striking deactivation of total CAT activity by AT in A. thaliana leaves largely results from the suppression of CAT1 isozyme, and that APX1, GR1, and a newly synthesized GR isozyme could complement the role of CAT1 to metabolize H_2O_2 into non-toxic water.
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