Structural study of the X-ray-induced enzymatic reduction of molecular oxygen to water by Steccherinum murashkinskyi laccase: insights into the reaction mechanism.

The laccase from Steccherinum murashkinskyi is a member of the 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. The reducing properties of X-ray radiation and the high quality of the laccase crystals allow the study of the catalytic reduction of dioxygen to water directly in a crystal. A series of diffraction data sets with increasing absorbed radiation dose were collected from a single crystal of Steccherinum murashkinskyi laccase at 1.35 Šresolution. Changes in the active-site structure associated with the reduction of molecular oxygen to water on increasing the absorbed dose of ionizing radiation were detected. The structures in the series are mixtures of different states of the enzyme-substrate complex. Nevertheless, it was possible to interpret these structures as complexes of various oxygen ligands with copper ions in different oxidation states. The results allowed the mechanism of oxygen reduction catalyzed by laccases to be refined.

[Comparative analysis of the ligninolytic potential of basidiomycetes belonging to different taxonomic and ecological groups].

Screening of the ligninolytic activity of basidiomycetes from the Culture Collection of the Komarov Botanical Institute, Russian Academy of Sciences, belonging to diterent taxonomic and ecological groups was performed. The patterns of the position of taxa of active producers of ligninolytic enzymes in the modern system of fungi were identified. Cluster analysis showed that the group of fungi with the greatest lign- inolytic and degradation potential includes representatives of the families Pleurotaceae, Polyporaceae, and Phanerochaetaceae, which perform the first stages of wood decomposition. As a result, species of interest for the further study of their oxidative potential and use in biotechnology were selected.