Characterization of two flavonol synthases with iron-independent flavanone 3-hydroxylase activity from Ornithogalum caudatum Jacq

Abstract

Background: Flavonol synthase (FLS) is the key enzyme responsible for the biosynthesis of flavonols, the most abundant flavonoids, which have diverse pharmaceutical effects. Flavonol synthase has been previously found in other species, but not yet in Ornithogalum caudatum. Results: The transcriptome-wide mining and functional characterisation of a flavonol synthase gene family from O. caudatum were reported. Specifically, a small FLS gene family harbouring two members, OcFLS1 and OcFLS2, was isolated from O. caudatum based on transcriptome-wide mining. Phylogenetic analysis suggested that the two proteins showed the closest relationship with FLS proteins. In vitro enzymatic assays indicated OcFLS1 and OcFLS2 were flavonol synthases, catalysing the conversion of dihydroflavonols to flavonols in an iron-dependent fashion. In addition, the two proteins were found to display flavanone 3β-hydroxylase (F3H) activity, hydroxylating flavanones to form dihydroflavonols. Unlike single F3H enzymes, the F3H activity of OcFLS1 and OcFLS2 did not absolutely require iron. However, the presence of sufficient Fe 2+ was demonstrated to be conducive to successive catalysis of flavanones to flavonols. The qRT-PCR analysis demonstrated that both genes were expressed in the leaves, bulbs, and flowers, with particularly high expression in the leaves. Moreover, their expression was regulated by developmental and environmental conditions. Conclusions: OcFLS1 and OcFLS2 from O. caudatum were demonstrated to be flavonol synthases with ironindependent flavanone 3-hydroxylase activity.

Two putative parallel pathways for naringenin biosynthesis in Epimedium wushanense

“…The stereo purity of the avonoids is also vital for their preclinical activity in various aspects of pharmaceutical use. 14,51 CHILs have shown their vital role as auxiliary proteins by interacting with CHS or CHI to enhance protein-protein interactions and stabilise chalconoids, therefore maintaining the substrate specicity of CHS. 48 Among the two types of CHILs, type III CHILs exhibit binding activity towards fatty acids, and hence play a role in fatty acid metabolism.…”

Naringenin confers defence against Phytophthora nicotianae through antimicrobial activity and induction of pathogen resistance in tobacco

“…Among all plant secondary metabolites, flavonoids are widely studied as they have a multitude of biological functions, including a function as defence molecules against biotic and abiotic stresses (Treutter, 2005; Zhang et al, 2020). Flavanones and flavonols are categories of flavonoids that differ by a hydroxyl moiety in the 3′ position in flavonols that is lacking in flavanones (Sun et al, 2019). Flavanones include phloretin, glyceollins and naringenin.…”

De novo biosynthesis of garbanzol and fustin in Streptomyces albus based on a potential flavanone 3‐hydroxylase with 2‐hydroxylase side activity

“…supplemented with naringenin because the heterologous expression of a gene encoding the Medicago truncatula FNSII led to flavone production in vivo , but it only yielded 2‐hydroxynaringenin in vitro (Akashi et al ., 1999; Zhang et al ., 2007). The side activity of some flavonoid enzymes is not entirely new; in fact, it has been described that some FLSs present F3H activity, despite the low homology that exists between both enzymes (Prescott et al ., 2002; Duan et al ., 2017; Park et al ., 2019; Sun et al ., 2019).…”