Molecular characterization of the enzyme catalyzing the aryl migration reaction of isoflavonoid biosynthesis in soybean

The first specific reaction in the biosynthesis of isoflavonoid compounds i n plants is the a-hydroxylation, coupled to aryl migration, of a flavanone. Using a functional genomics approach, we have characterized a cDNA encodin g a 2-hydroxyisoflavanone synthase from soybean (Glycine max). Microsomes i solated from insect cells expressing this cytochrome P450 from a baculoviru s vector convert 4',7-dihydroxyflavanone (liquiritigenin) to 4',7-dihydroxy isoflavone (daidzein), most likely via 2,4',7-trihydroxyisoflavanone which spontaneously dehydrates to daidzein. The enzyme also converts naringenin ( 4',5,7-trihydroxyflavanone) to genistein, but at a lower rate. 2-Hydroxyiso flavanone synthase transcripts are strongly induced in alfalfa cell suspens ions in response to elicitation. (C) 1999 Academic Press.