Catechol oxidases (EC 22.214.171.124) catalyse the oxidation of o-diphenols to their corresponding o-quinones. These oxidases contain two copper ions (CuA and CuB) within the so-called coupled type 3 copper site as found in tyrosinases (EC 126.96.36.199) and haemocyanins. The crystal structures of a limited number of bacterial and fungal tyrosinases and plant catechol oxidases have been solved. In this study, we present the first crystal structure of a fungal catechol oxidase from Aspergillus oryzae (AoCO4) at 2.5-Å resolution. AoCO4 belongs to the newly discovered family of short-tyrosinases, which are distinct from other tyrosinases and catechol oxidases because of their lack of the conserved C-terminal domain and differences in the histidine pattern for CuA. The sequence identity of AoCO4 with other structurally known enzymes is low (less than 30 %), and the crystal structure of AoCO4 diverges from that of enzymes belonging to the conventional tyrosinase family in several ways, particularly around the central α-helical core region. A diatomic oxygen moiety was identified as a bridging molecule between the two copper ions CuA and CuB separated by a distance of 4.2–4.3 Å. The UV/vis absorption spectrum of AoCO4 exhibits a distinct maximum of absorbance at 350 nm, which has been reported to be typical of the oxy form of type 3 copper enzymes.
- binuclear copper site
- catechol oxidase
- type 3 copper enzymes
- x-ray crystallography
Hakulinen, N., Gasparetti, C., Kaljunen, H., Kruus, K., & Rouvinen, J. (2013). The crystal structure of an extracellular catechol oxidase from the ascomycete fungus Aspergillus oryzae. Journal of Biological Inorganic Chemistry, 18(8), 917-929. https://doi.org/10.1007/s00775-013-1038-9