Thioltransferase from Schizosaccharomyces pombe: purification to homogeneity and some properties

Two types of thioltransferase were identified in the cytosolic extract of Schizosaccharomyces pombe, a fission yeast. In the present study, the major one of them was purified to homogeneity using chromatography processes such as ion-exchange chromatography and gel filtration. Purification was monitored by the transhydrogenase activity of thioltransferase with 2-hydroxyethyl disulfide as a substrate. Its molecular weight was estimated to be about 14,000 on SDS-polyacrylamide gel electrophoresis. The purified enzyme catalyzes the reduction of various disulfide compounds such as S-sulfocysteine, L-cystine, and insulin. It was also found to contain the reducing activity on non-disulfide substrates such as dehydroascorbic acid and alloxan. Its activity was greatly activated by high concentrations of reduced glutathione. It was found to be very heat-stable as like other thioltransferases. It was characterized on other aspects such as kinetic parameters and optimal reaction conditions.