LIGNIN PEROXIDASE ISOZYMES FROM PHANEROCHAETE-CHRYSOSPORIUM CAN BE ENZYMATICALLY DEPHOSPHORYLATED

The extracellular lignin peroxidase (LIP) protein profile of the fungu s Phanerochaete chrysosporium, grown in nonimmersed liquid culture und er conditions of excess nitrogen, changed markedly with culture age, A t peak LIP activity (day 4), the heme-protein profile in the extracell ular fluid, analyzed by anion-exchange high-pressure liquid chromatogr aphy, was characterized by a predominance of the LIP isozymes H1 and H 2, small amounts of H6 and H8, and other minor peaks, designated Ha an d Hb. On day 5, the level of H1 increased and it became the dominant i sozyme, with a corresponding decrease in the level of H2, Moreover, th e relative levels of H6 and H8 decreased with corresponding increases in Ha and Hb levels, This change in LIP profile occurred extracellular ly and resulted from the enzymatic dephosphorylation of LIP isozymes, An enzymatic fraction responsible for LIP isozyme dephosphorylation, t ermed LIP dephosphorylating (LpD) fraction, was partially purified fro m the culture fluid, Incubation of the LpD fraction with P-32-labeled H2, H6, H8, and H10 isozymes separated from nitrogen-limited cultures resulted in the formation of the dephosphorylated isozymes H1, Ha, Hb, and Hc, respectively, Dephosphorylation did not significantly change the catalytic properties of the LIP isozymes with veratryl alcohol as a substrate, LIP dephosphorylation is therefore suggested to be a post translational modification process catalyzed extracellularly by the Lp D activity.