Laccase-catalyzed oxidation of natural compounds

Laccases are copper-containing oxidoreductases which catalyze the oxidation of a variety of substrates with the concomitant reduction of molecular oxygen to water. Besides their technological exploitation in textile, dye and printing industries, these enzymes have been recently employed for the selective modification of different natural compounds. Typical substrates of laccases are phenols and aliphatic or aromatic amines, the reaction products being mixtures of dimers or oligomers derived by the coupling of the reactive radical intermediates. Additionally, non-phenolic groups, particularly benzyl and - more generally - primary alcohols, can be oxidized by laccases due to the ancillary action of the so-called "mediators" (i.e., TEMPO, HBT, ABTS). Recently, coupled laccase-mediator systems have been successfully employed for the regioselective oxidation of different sugar derivatives and natural glycosides.