Characterization of three flavonol synthases involved in the biosynthesis of 4'-deoxyflavonol in <i>Scutellaria baicalensis</i> Georgi

<italic>Scutellaria baicalensis</italic> Georgi is a traditional Chinese medicinal herb that is rich in 4'-deoxyflavonoids. Galangin (4'-deoxyflavonol) is a bioactive natural product found in <italic>S. baicalensis</italic>. To date, little is known about the biosynthesis of galangin. In this study, three flavonol synthases, Sb2ODD8, Sb2ODD11, and Sb2ODD12 were characterized from <italic>S. baicalensis</italic>. They exhibited bifunctional F3H/FLS activities (predominantly FLS), converting flavanones to dihydroflavonols, and then to flavonols. Enzyme kinetics revealed that they had distinct substrate preferences: Sb2ODD11 showed higher catalytic efficiency towards pinobanksin (4'-deoxydihydroflavonol), while Sb2ODD8 and Sb2ODD12 preferred dihydrokaempferol (4'-hydroxydihydroflavonol). These findings provide insights into the biosynthesis of flavonols in <italic>S. baicalensis</italic> and offer valuable information for metabolic engineering of flavonol production.