PURIFICATION AND CHARACTERIZATION OF GLUTAREDOXIN FROM CRYPTOCOCCUS-NEOFORMANS

Glutaredoxin, also known as thioltransferase, was purified from Crypto coccus neoformans by procedures including DEAE-cellulose ion exchange chromatography, Q-Sepharose ion-exchange chromatography, and gel filtr ation on Sephadex G-50. Its purity was confirmed by SDS-polyacrylamide gel electrophoresis and its molecular weight was estimated to be 12,0 00 Da. The purified enzyme has a Km value of 1.03 mM with 2-hydroxyeth yl disulfide as a substrate. The enzyme also utilizes L-sulfocysteine, L-cystine, and bovine serum albumin as substrates in the presence of reduced glutathione. The enzyme has Km values of 0.34-2.50 mM for thes e substrates. It was greatly activated by thiol compounds such as redu ced glutathione, dithiothreitol, L-cysteine and beta-mercaptoethanol. It is partially inactivated at 60 degrees C or higher temperatures. It plays an important role in thiol-disulfide exchange in Cryptococcus n eoformans.