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Laccases are enzymes that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of molecular oxygen to water. Here, a subatomic resolution X‐ray crystallographic study of the mechanism of inhibition of the laccase from the basidiomycete fungus Steccherinum murashkinskyi by chloride and fluoride ions is presented. Three series of X‐ray diffraction data sets were collected with increasing doses of absorbed X‐ray radiation from a native S. murashkinskyi laccase crystal and from crystals of complexes of the laccase with chloride and fluoride ions. The data for the native laccase crystal confirmed the previously deduced enzymatic mechanism of molecular oxygen reduction. The structures of the complexes allowed the localization of chloride and fluoride ions in the channel near the T2 copper ion. These ions replace the oxygen ligand of the T2 copper ion in this channel and can play the role of this ligand in the enzymatic reaction. As follows from analysis of the structures from the increasing dose series, the inhibition of laccases by chloride and fluoride anions can be explained by the fact that the binding of these negatively charged ions at the position of the oxygen ligand of the T2 copper ion impedes the reduction of the T2 copper ion. [ABSTRACT FROM AUTHOR]

Laccases are multicopper oxidases that catalyze oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of dioxygen to water. The physicochemical and catalytic properties of two new fungal laccases from basidiomycetes Antrodiella faginea (AfL) and Steccherinum murashkinskyi (SmL) with middle redox potential of the T1 copper site were studied. The X-ray structures of AfL and SmL were solved at 1.75 Å and 0.95 Å, respectively. The oxidized state of copper ions in the active site was observed in AfL structure, while the mixture of oxidized and reduced states was observed in SmL structure. These oxidized and reduced states relate to the position of copper ions, their coordination, and nature and position of oxygen ligands. Comparative analysis of the T1 site environment of laccases with known structure allowed us to highlight the six types of the secondary coordination sphere of the T1 copper. The solvent accessible surface area of the conservative region of the secondary coordination sphere of the T1 copper correlates with its the redox potential. It was shown that the laccase classification by the structure of the T1 copper secondary coordination sphere is in agreement to ecophysiological behavior of laccase producing fungi. [ABSTRACT FROM AUTHOR]

Laccases are members of a large family of multicopper oxidases that catalyze the oxidation of a wide range of organic and inorganic substrates accompanied by the reduction of dioxygen to water. A new laccase was isolated from the basidiomycete Coriolopsis caperata strain 0677 and its amino-acid sequence was determined. According to its physicochemical properties and spectroscopic features, the laccase from C. caperata is a high redox-potential blue laccase. Attempts to crystallize the native enzyme were unsuccessful. The copper type 2-depleted (T2D) laccase was prepared and crystallized. The structure of T2D laccase from C. caperata was solved at 1.6 Å resolution, and attempts to reconstruct the T2 copper centre were performed using Cu+ and Cu2+ ions. The structure of T2D+Cu+ laccase was solved at 1.89 Å resolution. It was shown that the T2D+Cu+ laccase structure contained four copper ions in the active site. Reconstruction could not be achieved when the T2D laccase crystals were treated with CuSO4. [ABSTRACT FROM AUTHOR]

Laccases, blue copper-containing oxidases, ≿an play an important role in a variety of natural processes. The majority of fungal laccases are encoded by multigene families that express closely related proteins with distinct functions. Currently, only the properties of major gene products of the fungal laccase families have been described. Our study is focused on identification and characterization of laccase genes, which are transcribed in basidiomycete Trametes hirsuta 072 , an efficient lignin degrader, in a liquid medium, both without and with induction of laccase transcription by copper ions. We carried out production of cDNA libraries from total fungal RNA, followed by suppression subtractive hybridization and mirror orientation selection procedures, and then used Next Generation Sequencing to identify low abundance and differentially expressed laccase transcripts. This approach resulted in description of five laccase genes of the fungal family, which, according to the phylogenetic analysis, belong to distinct clusters within the Trametes genus. Further analysis established similarity of physical, chemical, and catalytic properties between laccases inside each cluster. Structural modeling suggested importance of the sequence differences in the clusters for laccase substrate specificity and catalytic efficiency. The implications of the laccase variations for the fungal physiology are discussed. [ABSTRACT FROM AUTHOR]