Growth of Irpex lacteus on polyurethane solid support led to secretion of various manganese-dependent peroxidase (MnP) isoenzymes with pI in the range of 3.8-6.7. The highest MnP activity was obtained at 8.9 mmol l(-1) Mn2+. when predominantly a pI 4.8 isoenzyme was produced. Optimization of anion exchange chromatography (Mono Q) allowed the separation of MnP isoenzymes and collection of extensive sequence information by tandem LC-MS. The pI 4.8 isoenzyme was purified 109-fold (6% activity yield) by ion exchange chromatography, its specific activity of Mn2+ oxidation was 2800 nkat mg(-1), molecular mass 37 kDa and pH optimum 5. The other properties were: respective half-lives (pH 4.5) of 575, 325 and 7 min at 40, 50 and 60 C, K-m, values 46.7; 9.5; 21.4 mu mol l(-1) and k(cat) values 69.0; 64.2; 15.7 s(-1) for Mn2+, H2O2 and DMP with Mn2+, respectively. The pI4.8 isoenzyme was shown to be a true MnP affecting secondary substrates via the oxidation of Mn2+. Its biochemical properties and production by I. lacteus make the enzyme a candidate for biotechnological applications. (C) 2010 Elsevier Inc. All rights reserved.