Dioxygenase, Flavonoid Biosynthesis, Flavonols, Matthiola incana Soluble enzyme preparations from flower buds of Matthiola incana catalysed the conversion of dihydrokaempferol to kaempferol and of dihydroquercetin to quercetin. The reaction required 2-oxoglutarate, ascorbate and Fe2+ as cofactors and had a pH-optimum at about 7.0. Highest enzyme activity was already present in the youngest buds...