C-2 and C-3 oxidation of d-Glc, and C-2 oxidation of d-Gal by pyranose dehydrogenase from Agaricus bisporus

The quinone-dependent sugar oxidoreductase, pyranose dehydrogenase purified from the basidiomycete Agaricus bisporus catalyzed C-2 and C-3 oxidation of d-Glc to d-arabino-hexos-2-ulose (2-keto-d-Glc) and, preferentially, d-ribo-hexos-3-ulose (3-keto-d-Glc). The two aldoketoses accumulated only transiently in the reaction mixture being continually converted to the same end-product, d-erythro-hexos-2,3-diulose (2,3-diketo-d-Glc). d-Gal was oxidized by pyranose dehydrogenase and 1,4-benzoquinone exclusively at C-2 to produce d-lyxo-hexos-2-ulose (2-keto-d-Gal). Structures of the enzyme reaction products were deduced from their N,N-diphenylhydrazone derivatives.