title: Biochemical and molecular characterization of an atypical manganese peroxidase of the litter-decomposing fungus Agrocybe praecox.
abstract: Agrocybe praecox is a litter-decomposing Basidiomycota species of the order Agaricales, and is frequently found in forests and open woodlands. A. praecox grows in leaf-litter and the upper soil and is able to colonize bark mulch and wood chips. It produces extracellular manganese peroxidase (MnP) activities and mineralizes synthetic lignin. In this study, the A. praecox MnP1 isozyme was purified, cloned and enzymatically characterized. The enzyme catalysed the oxidation of Mn(2+) to Mn(3+), which is the specific reaction for manganese-dependent class II heme-peroxidases, in the presence of malonate as chelator with an activity maximum at pH 4.5; detectable activity was observed even at pH 7.0. The coding sequence of the mnp1 gene demonstrates a short-type of MnP protein with a slightly modified Mn(2+) binding site. Thus, A. praecox MnP1 may represent a novel group of atypical short-MnP enzymes. In lignocellulose-containing cultures composed of cereal bran or forest litter, transcription of mnp1 gene was followed by quantitative real-time RT-PCR. On spruce needle litter, mnp1 expression was more abundant than on leaf litter after three weeks cultivation. However, the expression was constitutive in wheat and rye bran cultures. Our data show that the atypical MnP of A. praecox is able to catalyse Mn(2+) oxidation, which suggests its involvement in lignocellulose decay by this litter-decomposer.
authors.affiliation: Department of Food and Environmental Sciences, Viikki Biocenter, University of Helsinki, Finland; School of Biology, University of Nottingham, UK. Electronic address: kristiina.s.hilden@helsinki.fi.
authors.forename: Kristiina
authors.initials: K
authors.lastname: Hildén
authors.affiliation: Department of Food and Environmental Sciences, Viikki Biocenter, University of Helsinki, Finland.
authors.forename: Miia R
authors.initials: MR
authors.lastname: Mäkelä
authors.affiliation: Department of Food and Environmental Sciences, Viikki Biocenter, University of Helsinki, Finland.
authors.forename: Kari T
authors.initials: KT
authors.lastname: Steffen
authors.affiliation: Department of Bio- and Environmental Sciences, International Graduate School of Zittau, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Hofrichter
authors.affiliation: Department of Food and Environmental Sciences, Viikki Biocenter, University of Helsinki, Finland.
authors.forename: Annele
authors.initials: A
authors.lastname: Hatakka
authors.affiliation: School of Biology, University of Nottingham, UK.
authors.forename: David B
authors.initials: DB
authors.lastname: Archer
authors.affiliation: Department of Food and Environmental Sciences, Viikki Biocenter, University of Helsinki, Finland.
authors.forename: Taina K
authors.initials: TK
authors.lastname: Lundell
mesh_terms: D055362:Agrocybe / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D004043:Dietary Fiber / Q000378:metabolism / Q000382:microbiology; D004795:Enzyme Stability; D015870:Gene Expression; D020869:Gene Expression Profiling; D006863:Hydrogen-Ion Concentration; D008345:Manganese / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D004271:DNA, Fungal; D004043:Dietary Fiber; D011994:Recombinant Proteins; D008345:Manganese; D010544:Peroxidases; C051129:manganese peroxidase
keywords: Basidiomycete; Gene expression; Litter decomposition; Manganese peroxidase; RT-qPCR; Saprotroph