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KMID : 0368419980410040312
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Journal of Plant Biology
1998 Volume.41 No. 4 p.312 ~ p.317
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An f-Type Thioredoxin from Arabidopsis thaliana Leaves
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Kim, Tae Soo
Kim, Joon Chul/Jin, Chang Duck/Han, Tae Jin/Lim, Chang Jin
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Abstract
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Thioredoxin, a small redox protein with an active site disulfide/dithiol, is ubiquitous in bacteria, plants, and animals and functions as a reducing agent and modulator of enzyme activity. A thioredoxin has been purified to electrophoretic homogeneity from the leaves of Arabidopsis thaliana using procedures such as DE-52 ion exchange chromatography, Sephadex G-50 gel filtration, Q-Sepharose ion exchange chromatography, and DEAE-Sephadex A-25 chromatography. The purified thioredoxin was determined to be a single band on SDS-PAGE, and its molecular weight was estimated to be 21 KDa, which was much larger than those of most other known thioredoxins. It was proved to be an f-type thioredoxin, since it could activate fructose-l,6-bisphosphatase, but it could not activate NADP^(+)-malate dehydrogenase. As a protein disulfide reductase, it could reduce the disulfide bonds contained in insulin. As a substrate, it showed a ㎞ value of 20.2μM on Escherichia coli thioredoxin reductase, and it had an optimal pH of 8.0. The molecular weight of the purified f-type thioredoxin is not consistent with those of the five divergent h-type thioredoxins already identified by cDNA cloning. The purified f-type thioredoxin is the first example isolated from A. thaliana.
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