Purification and characterization of 17beta-hydroxysteroid dehydrogenase from the filamentous fungus Cochliobolus lunatus.

17beta-Hydroxysteroid dehydrogenase (17beta-HSD) from the filamentous fungus Cochliobolus lunatus was purified in three steps, yielding a protein of an apparent molecular mass of 28 kDa. According to the obtained experimental data, the native form of the enzyme could be a dimer (60 kDa) and/or a tetramer (120 kDa). The enzyme was found to catalyse preferentially the reduction of steroid substrates using NADPH as an electron donor. Both androgens and estrogens are substrates for 17beta-HSD. Kinetic studies revealed the equilibrium ordered kinetic mechanism with NADPH as the first ligand to be bound to the enzyme followed by the addition of the substrate androstenedione. The purification and characterization of 17beta-HSD from Cochliobolus lunatus represents a step towards the elucidation of the role of this enzyme in fungal metabolism.