A Second Thioltransferase of Schizosaccharomyces pombe Contains Glutathione S-transferase Activity

Two types of the thioltransferase (also called glutaredoxin) have been previously detected in the cytosolic extract of Schizosaccharomyces pombe, a fission yeast. Previously, the one with a smaller molecular mass (14 kDa) was purified and characterized. In the present study, the second thioltransferase was purified. The purification procedure included ammonium sulfate fractionation (40-80%), Sephadex G-200 gel nitration, DEAE-cellulose ion-exchange chromatography, Sephadex G-50 gel filtration, and glutathione-agarose affinity chromatography. The purified enzyme showed a single band on SDS-PAGE, and its molecular mass was determined to be 23 kDa. It utilizes various compounds as substrates, including 2-hydroxyethyl disulfide. Interestingly, we found that the purified thioltransferase also contains significant glutathione S-transferase activity.