Biochemical and molecular characterization of a laccase from the edible straw mushroom, Volvariella volvacea

Abstract

We have isolated a laccase (lac1) from culture fluid of Volvariella volvacea, grown in a defined medium containing 150 µm CuSO4, by ion‐exchange and gel filtration chromatography. Lac1 has a molecular mass of 58 kDa as determined by SDS/PAGE and an isoelectric point of 3.7. Degenerate primers based on the N‐terminal sequence of purified lac1 and a conserved copper‐binding domain were used to generate cDNA fragments encoding a portion of the lac1 protein and RACE was used to obtain full‐length cDNA clones. The cDNA of lac1 contained an ORF of 1557 bp encoding 519 amino acids. The amino acid sequence from Ala25 to Asp41 corresponded to the N‐terminal sequence of the purified protein. The first 24 amino acids are presumed to be a signal peptide. The expression of lac1 is regulated at the transcription level by copper and various aromatic compounds. RT‐PCR analysis of gene transcription in fungal mycelia grown on rice‐straw revealed that, apart from during the early stages of substrate colonization, lac1 was expressed at every stage of the mushroom developmental cycle defined in this study, although the levels of transcription varied considerably depending upon the developmental phase. Transcription of lac1 increased sharply during the latter phase of substrate colonization and reached maximum levels during the very early stages (primordium formation, pinhead stage) of fruit body morphogenesis. Gene expression then declined to ≈ 20–30% of peak levels throughout the subsequent stages of sporophore development.

Purification of a novel extracellular laccase from solid-state culture of the edible mushroom Lentinula edodes

“…Generally, Lccs occur as a series of isozymes encoded by a family of genes. Many Lcc isozymes have been purifi ed, and their encoding genes have been cloned from various white-rot basidiomycetes (Chen et al 2004;Hoegger et al 2004;Baldrian 2006). Lentinula edodes (Berk.)…”

Function and molecular evolution of multicopper blue proteins

“…Another white laccase, extracted from Phellinus ribis, binds two zinc ions, one manganese ion and one copper ion, and can oxidize various substrates [61]. Another strain of white laccase is found in Volvariella volvacea [62]. The presence of white laccase poses many questions.…”

Effect of Cu2+, Mn2+ and aromatic compounds on the production of laccase isoforms by Coprinus comatus

“…A range of enzymes are synthesized during mushroom growth on these substrates including laccases [benzenediol:oxygen oxidoreductases (EC 1.10.3.2)], copper-containing enzymes that catalyze the oxidation of a broad spectrum of phenolic compounds and non-phenolic substrates using molecular oxygen as the electron acceptor. Laccases are widely distributed among fungi, where they have been assigned roles in lignin degradation (Bourbonnais et al 1995;Eggert et al 1997), in rendering phenolic compounds less toxic via oxidative coupling and polymerisation (Bollag et al 1988; Moldes and Sanroman 2006) and in mushroom fruit-body morphogenesis (Zhao and Kwan 1999;Chen et al 2004). Laccases may be either constitutive or inducible, and many factors including culture parameters (Fu et al 1997), heavy metals (Baldrian and Gabriel 2002;Chen et al 2003) and aromatic compounds (Scheel et al 2000) are reported to influence enzyme production in different fungal species.…”