PURIFICATION AND CHARACTERIZATION OF GLUTAREDOXIN (THIOLTRANSFERASE) FROM RICE (ORYZA-SATIVA L)

We purified and characterized glutaredoxin (thioltransferase), which c atalyzes thiol/disulfide exchange reaction, for the first time in plan ts, The purification procedure employed an immunoabsorbent, antiglutar edoxin-Sepharose. Glutaredoxin was purified about 2,200-fold from rice bran and it appeared to be homogeneous on SDS-PAGE, MALDI-TOF mass sp ectrometry revealed that the protein has a molecular mass of 11,097.9 Da. Rice glutaredoxin consists of 105 amino acid residues, containing the tetrapeptide -Cys-Phe-Pro (Tyr)-Cys-, which constitutes the active site of Escherichia coli and mammalian glutaredoxins. Inactivation as say also indicated that cysteine residues are responsible for enzyme a ctivity, Kinetic analyses revealed that the enzyme did not exhibit nor mal Michaelis-Menten kinetics, The enzyme has an optimum pH of about 8 .7 with 2-hydroxyethyl disulfide as a substrate, In addition, rice glu taredoxin has dehydroascorbate reductase activity, like mammalian glut aredoxin.