EN
An intracellular glutathione transferase was purified to homogenity from the fungus, Mucor mucedo, using DEAE-cellulose ion-exchange and glutathione affinity chromatography. Gel filtration chromatography and SDS-PAGE revealed that the purified GST is a homodimer with approximate native and subunit molecular mass of 53 kDa and 23.4 kDa, respectively. The enzyme has a pI value of 4.8, a pH optimum at pH 8.0 and apparent activation energy (Ea) of 1.42 kcal mol⁻¹. The purified GST acts readily on CDNB with almost negligible peroxidase activity and the activity was inhibited by Cibacron Blue (IC₅₀ 0.252 μM) and hematin (IC₅₀ 3.55 μM). M. mucedo GST displayed a non-Michaelian behavior. At Iow (0.1-0.3 mM) and high (0.3-2 mM) substrate concentration, Km(GSH) was calculated to be 0.179 and 0.65 mM, whereas Km(CDNB) was 0.531 and 11 mM and kcat was 39.8 and 552 s⁻¹, respectively. The enzyme showed apparent pKa values of 6-6.5 and 8.0.