Purification and characterization of an extracellular Mn(II)-dependent peroxidase from the lignin-degrading basidiomycete, Phanerochaete chrysosporium

A Mn(II)-dependent peroxidase found in the extracellular medium of ligninolytic cultures of the white rot fungus, Phanerochaete chrysosporium, was purified by DEAE-Sepharose ion-exchange chromatography, Blue Agarose chromatography, and gel filtration on Sephadex G-100. Sodium dodecyl sulfate-gel electrophoresis indicated that the homogeneous protein has an Mr of 46,000. The absorption spectrum of the enzyme indicates the presence of a heme prosthetic group. The pyridine hemochrome absorption spectrum indicates that the enzyme contained one molecule of heme as iron protoporphyrin IX. The absorption maximum of the native enzyme (406 nm) shifted to 433 nm in the reduced enzyme and to 423 nm in the reduced-CO complex. Both CN- and N-3 readily bind to the native enzyme, indicating an available coordination site and that the heme iron is high spin. The absorption spectrum of the H2O2 enzyme complex, maximum at 420 nm, is similar to that of horseradish peroxidase compound II. P. chrysosporium peroxidase activity is dependent on Mn(II), with maximal activity attained above 100 microM. The enzyme is also stimulated to varying degrees by alpha-hydroxy acids (e.g., malic, lactic) and protein (e.g., gelatin, albumin). The peroxidase is capable of oxidizing NADH and a wide variety of dyes, including Poly B-411 and Poly R-481. Several of the substrates (indigo trisulfonate, NADH, Poly B-411, variamine blue RT salt, and Poly R-481) are oxidized by this Mn(II)-dependent peroxidase at considerably faster rates than those catalyzed by horseradish peroxidase. The enzyme rapidly oxidizes Mn(II) to Mn(III); the latter was detected by the characteristic absorption spectrum of its pyrophosphate complex. Inhibition of the oxidation of the substrate diammonium 2,2-azino-bis(3-ethyl-6-benzothiazolinesulfonate) (ABTS) by Na-pyrophosphate suggests that Mn(III) plays a role in the enzyme mechanism.