An L-type thioltransferase from Arabidopsis thaliana leaves

Thioltransferase, also called glutaredoxin, is a general GSH-disulfide reductase of importance for redox regulation. Previously, the protein thioltransferase, now called S-type thioltransferase, was purified and characterized from Arabidopsis thaliana seed. In the present study, a second thioltransferase, called L-type thioltransferase, was purified to homogeneity from Arabidopsis thaliana leaves, The purification procedures included DEAE-cellulose ion-exchange chromatography, Sephadex G-50 gel filtration, and glutathione-agarose affinity chromatography, The purified enzyme was confirmed to show a unique band on SDS-PAGE and its molecular weight was estimated to be 26.6 kDa, which appeared to be atypical compared with those of most other thioltransferases. It could utilize 2-hydroxyethyl disulfide, S-sulfocysteine, and insulin as substrates, and also contained dehydroascorbate reductase activity. Its optimum pH was 8.5 and its activity was greatly activated by L-cysteine. When it was kept for 30 min, it appeared to be very stable up to 70 degrees C, It was activated by MgCl2 and, on the contrary, inhibited by ZnCl2, MnCl2, and AlCl3.