Post-aromatic deoxygenation in polyketide biosynthesis: reduction of aromatic rings in the biosyntheses of fungal melanin and anthraquinone.

Two enzyme reactions involved in the post-aromatic deoxygenation process of fungal melanin and pigments were studied from the viewpoint of enzymic reduction of aromatic rings. Hydroxynaphthalene reductase that catalyzes reduction of the aromatic rings of 1,3,6,8-tetrahydroxynaphthalene and 1,3,8-trihydroxynapthalene was partially purified from Phialophora lagerbergii and characterized. Emodin deoxygenase of Pyrenochaeta terrestris that catalyzes deoxygenation of emodin to afford chrysophanol was found to be resolved into two protein fractions with DEAE-cellulose column. The two protein fractions acted synergistically in regard to emodin deoxygenase activity.