EXTRACELLULAR PROTEASES PRODUCED BY THE WOOD-DEGRADING FUNGUS PHANEROCHAETE-CHRYSOSPORIUM UNDER LIGNINOLYTIC AND NON-LIGNINOLYTIC CONDITIONS

When subjected to nitrogen limitation, the wood-degrading fungus Phane rochaete chrysosporium produces two groups of secondary metabolic, ext racellular isoenzymes that depolymerize lignin in wood: lignin peroxid ases and manganese peroxidases. We have shown earlier the turnover in activity of the lignin peroxidases to be due in part to extracellular proteolytic activity. This paper reports the electrophoretic character ization of two sets of acidic extracellular proteases produced by subm erged cultures of P. chrysosporium. The protease activity seen on day 2 of incubation, during primary growth when nitrogen levels are not kn own to be limiting, consisted of at least six proteolytic bands rangin g in size from 82 to 22 kDa. The activity of this primary protease was strongly reduced in the presence of SDS. Following the day 2, when ni trogen levels are known to become limiting and cultures become lignino lytic, the main protease activity (secondary protease) consisted of a major proteolytic band of 76 kDa and a minor band of 25 kDa. The major and minor secondary protease activities were inhibited by phenylmethy lsulfonyl fluoride and pepstatin A, respectively. When cultures were g rown in the presence of excess nitrogen (nonligninolytic condition), t he primary protease remained the principal protease throughout the cul ture period. These results identify and characterize a specific proteo lytic activity associated with conditions that promote lignin degradat ion.