Involved in C-Ring Modifications

This enzyme catalyzes the stereospecific conversion of the (2R, JR)-dihydroflavonols, DHK and DHQ, to the corresponding flavonols, by introducing a double bond between C-2 and C-3. The enzyme was first reported in parsley cell cultures,58 and later shown to occur in several plant species.7 A cDNA clone encoding FLS was isolated from Petunia hybridal and its antisense expression strongly reduced flavonol synthesis in flower petals, thus allowing a higher flux of dihydroflavonols to be channeled towards anthocyanin synthesis.59 

This enzyme catalyzes the conversion of flavan 3,4-diols (leucoanthocyanidins) to their corresponding anthocyanidins.60 A cDNA encoding ANS was recently isolated from Perilla frutescens,61 and its recombinant protein catalyzed the oxidation of both leucocyanidin and leucopelargonidin to their corresponding anthocyanidins, most likely via their 2-flaven-3,4-diols upon subsequent acidification. The enzyme exhibited a 3-fold higher affinity for leucocyanidin over leucopelargonidin.61 Leucodelphinidin was not tested as a substrate. 

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