Abstract
A high-efficiency laccase, DLac, was isolated from Cerrena sp. RSD1. The kinetic studies indicate that DLac is a diffusion-limited enzyme. The crystal structure of DLac was determined to atomic resolution, and its overall structure shares high homology to monomeric laccases, but displays unique substrate-binding loops from those in other laccases. The substrate-binding residues with small side chain and the short substrate-binding loop IV broaden the substrate-binding cavity and may facilitate large substrate diffusion. Unlike highly glycosylated fungal laccases, the less-glycosylated DLac contains one highly conserved glycosylation site at N432 and an unique glycosylation site at N468. The N-glycans stabilize the substrate-binding loops and the protein structure, and the first N-acetylglucosamine is crucial for the catalytic efficiency. Additionally, a fivefold increase in protein yield is achieved via the submerged culture method for industrial applications. Database: The atomic coordinates of the structure of DLac from Cerrena sp. RSD1 and structural factors have been deposited in the RCSB Protein Data Bank (PDB ID: 5Z1X).