Intracellular ferrireductase involved in Mn(IV)-educting enzyme enzyme system to supply Mn(II) for lignin biodegradation by white-rot fungus Phanerochaete sordida YK-624

摘要

In the biobleaching of kraft pulp with white-rot Phanerochaete sordida YK-624, it was confirmed that manganese dioxide (Mn(IV)) in kraft pulp was reduced to Mn(II) by ESR analysis.By this reactions, the production of manganese peroxidase (MnP) by P.sordida YK-624 was triggered and then the kraft pulp was bleached with MnP. In the liquid culture, the reduction of manganese dioxide was observed by the washed mycelia of P.sordida YK-624 although smaller amount of Mn(II) was produced by the extracellular culture fluid.The reduction by the washed mycelia was dependent on Fe(II), a metal chlator ,and NAD(P)H. Moreover, the cell-free extract from P.Sordida YK-624 catalyzed the reduction of ferric chelate to ferrous chelate in the presence of NAD(P)H. It is likely , therefore , that ferrous chelate reduce manganese dioxide and that the produced ferric chelate is reduced by intracellular NAD(P)H-dependent, that ferrous chelate reduces manganese dioxide and that the produced ferric chelate is reduced by intracellular NAD(P)H-dependent reductase to regenerate ferrous chelate. An intracellular NADPH-dependent reducate , anmely NADPH-dependent ferrireductase (molecular weight 35 kDa, pI 5.1), was purified from P.sordida YK-624 .Moreover, there was a good correlation between the production of intracellular ferrireductase and that of extracellular MnP in a liquid culture containing manganese dioxide. These results suggest that the ferrireductase is involved in the production of MnP by the reduction of manganese dioxide to Mn(II)