Thioltransferase from Arabidopsis thaliana Seed: Purification to Homogeneity and Characterization

초록

Thioltransferase is a general GSH-disulfide reductase of importance for redox regulation. The protein thioltransferase has been purified to apparent homogeneity on SDS-PAGE from the Arabidopsis thaliana seed. The purification procedures included DEAE-cellulose ion exchange chromatography, Sephadex G-75 gel filtration, Q-Sepharose ion exchange chromatography, and DEAE-Sephadex A-25 ion exchange chromatography. The enzyme has a molecular mass of 22 kDa and a pi of 4.8, and it is heatstable. The protein had broad specificities for substrates ranging from low-molecular disulfides (S-sulfocysteine and cystine) to protein disulfides (trypsin and insulin). However, it could not reduce the disulfide linkages of ribonuclease A and bovine serum albumin. It could utilize non-disulfide substrates such as dehydroascorbic acid and alloxan. The protein can reduce the disulfide bond in 2-hydroxyethyl disulfide with an optimum pH of 8.5. Its activity was greatly activated by monothiol compounds such as reduced glutathione and L-cysteine.

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