Expression of industrially relevant laccases: prokaryotic style

Laccases are a class of multi-copper oxidases (MCOs) that catalyze the one-electron oxidation of four equivalents of a reducing substrate, with the concomitant four-electron reduction of dioxygen to water. They can catalyze a multitude of reactions, including the degradation of polymers and oxidative coupling of phenolic compounds, positioning them as significant industrial enzymes. Although fungal laccases are well known and well characterized, only recently has in silico biology led to rapid advances in the discovery, characterization and engineered expression of prokaryotic laccases. We describe the recent burgeoning of prokaryotic laccases, their catalytic properties, structural features and molecular evolution, vis-à-vis fungal laccases where possible. Special focus is given to the application of laccases to the emerging cellulosic biofuel industry.