OXALATE-DEPENDENT REDUCTIVE ACTIVITY OF MANGANESE PEROXIDASE FROM PHANEROCHAETE-CHRYSOSPORIUM

The mechanism of oxalate-dependent reductive activity of a manganese-d ependent peroxidase (MnP) from Phanerochaete chrysosporium was investi gated. Ferric iron reduction was demonstrated in reaction mixtures con taining Mn-peroxidase, Mn2+, oxalate, H2O2, ferric chloride, and 1,10- phenanthroline. Only catalytic amounts of H2O2 were required. Oxygen c onsumption was also observed in reaction mixtures containing Mn-peroxi dase, Mn2+, oxalate, and H2O2 and was inhibited by the addition of fer ric iron. Electron spin resonance studies, using the spin traps 5,5-di methyl-1-pyrroline-N-oxide and alpha-4-pyridyl-1-oxide-N-t-butylnitron e were used to obtain evidence for the production of the formate radic al (CO2.-) and superoxide (O-2(.-)) in a reaction mixture containing M n2+, oxalate and H2O2. It was concluded that both CO2.- (anaerobic con ditions) and O-2(.-) (aerobic conditions) could reduce ferric iron. Th e dismutation of some O-2(.-) would produce H2O2 to provide a constant supply of H2O2. (C) 1994 Academic Press, Inc.