Fungal metabolism of flavonoids. Purification, properties, and substrate specificity of an inducible laccase from Polyporus versicolor PRL 572

Laccase (o-diphenol: O 2 oxidoreductase, EC 1.10.3.1) was obtained from culture filtrates of P. versicolor grown under a variety of conditions. The effect of gratuitous and nongratuitous inducers was examined and the general characteristics of the enzyme are reported. Purification of the enzyme, including the separation of two isoenzymic forms on DEAE-Sephadex A-50, and the substrate specificity of the two forms, are described.Kinetic data indicated that the enzyme had a higher affinity for flavonoid compounds than substituted phenols and phenylenediamines. To act as a substrate, flavonoids did not require a saturated C-2—C-3 bond, but did require a substituent at the C-3 position and a phenyl group at the C-2 position. Highest activity was obtained using flavonols as substrates. Flavonols glycosylated at the C-3 position were oxidized more slowly than the parent aglycon. No correlation was observed between the pattern of flavonol hydroxylation or flavonol glycosylation and ability to act as a substrate.