title: Effects of Mn2+ and oxalate on the catalatic activity of manganese peroxidase.
abstract: Manganese peroxidase from Phanerochaete chrysosporium is an extracellular heme-containing enzyme known to catalyze the oxidation of Mn2+ to Mn3+ in a reaction requiring oxalate or another appropriate manganese chelator. We have found that the enzyme can also catalyze a manganese-dependent disproportionation of hydrogen peroxide when a manganese chelator is not included. The catalatic activity was observed in the pH range from 3.0 to 8.5, and the apparent second-order rate constant for catalatic reaction was about 2 x 10(5) M-1 s-1 at pH 4.5 to 7.0 at 25 degrees C. Oxalate inhibited oxygen production by increasing the apparent K(m) for Mn2+ for catalatic activity from micromolar to millimolar levels and facilitating peroxidase activity. Catalase-type function was recovered by excess of Mn2+ in the presence of oxalate. We propose that catalatic activity may protect the enzyme from inactivation by hydrogen peroxide in an environment where free oxalate may be limited.
authors.affiliation: Biotechnology Center, Utah State University, Logan 84322-4705, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Timofeevski
authors.forename: S D
authors.initials: SD
authors.lastname: Aust
mesh_terms: D000818:Animals; D001487:Basidiomycota / Q000201:enzymology; D002374:Catalase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008345:Manganese / Q000378:metabolism* / Q000494:pharmacology; D010070:Oxalates / Q000378:metabolism* / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D010544:Peroxidases / Q000187:drug effects / Q000378:metabolism*
chemical_list: D010070:Oxalates; D008345:Manganese; D010544:Peroxidases; C042858:lignin peroxidase; C051129:manganese peroxidase; D002374:Catalase; D010100:Oxygen