Fungal pyranose oxidases: occurrence, properties and biotechnical applications in carbohydrate chemistry

Pyranose oxidases are widespread among lignin-degrading white rot fungi and are localized in the hyphal periplasmic space. They are relatively large f lavoproteins which oxidize a number of common monosaccharides on carbon-2 i n the presence of oxygen to yield the corresponding 2-keto sugars and hydro gen peroxide. The preferred substrate of pyranose oxidases is D-glucose whi ch is converted to 2-keto-D-glucose. While hydrogen peroxide is a cosubstra te in ligninolytic reactions, 2-keto-D-glucose is the key intermediate of a secondary metabolic pathway leading to the antibiotic cortalcerone. The fi nding that 2-keto-D-glucose can serve as an intermediate in an industrial p rocess for the conversion of D-glucose into D-fructose has stimulated resea rch on the use of pyranose oxidases in biotechnical applications. Unique ca talytic potentials of pyranose oxidases have been discovered which make the se enzymes efficient tools in carbohydrate chemistry. Converting common sug ars and sugar derivatives with pyranose oxidases provides a pool of sugar-d erived intermediates for the synthesis of a variety of rare sugars, fine ch emicals and drugs.