Dependence on freezing of the geometry and redox potential of type 1 and type 2 copper sites of Japanese-lacquer-tree (Rhus vernicifera) laccase

Abstract

The room-temperature EPR spectrum of the Japanese-lacquer-tree (R. vernicifera) laccase shows A.dblvert. (the hyperfine splitting constant) and g.dblvert. values of both the type 1 and type 2 Cu appreciably different from those measured at liquid-N2 temperature. The geometry of the sites, as inferred from the room-temperature EPR parameters, is more consistent with their redox properties. A rough correlation is found between A.dblvert. and g.dblvert. values and redox potential of the blue Cu in several enzymes.