THIOLTRANSFERASE FROM ARABIDOPSIS-THALIANA SEED - PURIFICATION TO HOMOGENEITY AND CHARACTERIZATION

Thioltransferase is a general GSH-disulfide reductase of importance fo r redox regulation. The protein thioltransferase has been purified to apparent homogeneity on SDS-PAGE from the Arabidopsis thaliana seed. T he purification procedures included DEAE-cellulose ion exchange chroma tography, Sephadex G-75 gel filtration, Q-Sepharose ion exchange chrom atography, and DEAE-Sephadex A-25 ion exchange chromatography, The enz yme has a molecular mass of 22 kDa and a pi of 4.8, and it is heatstab le, The protein had broad specificities for substrates ranging from lo w-molecular disulfides (S-sulfocysteine and cystine) to protein disulf ides (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, Th e protein can reduce the disulfide bond in 2-hydroxyethyl disulfide wi th an optimum pH of 8.5. Its activity was greatly activated by monothi ol compounds such as reduced glutathione and L-cysteine.