Molecular Characterization of the Enzyme Catalyzing the Aryl Migration Reaction of Isoflavonoid Biosynthesis in Soybean

• Published in: Archives of biochemistry and biophysics 1999-07, Vol.367 (1), p.146-150
• Main Authors: Steele, Christopher L., Gijzen, Mark, Qutob, Dinah, Dixon, Richard A.
• Format: Article
• Language: English
• Subjects: 2-hydroxyisoflavanone synthase; Amino Acid Sequence; amino acid sequences; Animals; Cloning, Molecular; complementary DNA; Expressed Sequence Tags; Flavanones; Flavonoids - metabolism; Gene Expression Regulation, Plant; Genistein - metabolism; Glycine max; Glycine max - cytology; Glycine max - enzymology; Glycine max - genetics; Hydroxylation; Insecta - cytology; Insecta - genetics; isoflavone synthase; Isoflavones - metabolism; Kinetics; Medicago sativa - cytology; Medicago sativa - enzymology; Medicago sativa - genetics; Microsomes - enzymology; Microsomes - metabolism; Molecular Sequence Data; nucleotide sequences; Oxygenases - chemistry; Oxygenases - genetics; Oxygenases - metabolism; phytoalexin; phytoalexins; Recombinant Proteins - biosynthesis; Recombinant Proteins - metabolism
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1006/abbi.1999.1238

The first specific reaction in the biosynthesis of isoflavonoid compounds in plants is the 2-hydroxylation, coupled to aryl migration, of a flavanone. Using a functional genomics approach, we have characterized a cDNA encoding a 2-hydroxyisoflavanone synthase from soybean (Glycine max). Microsomes isolated from insect cells expressing this cytochrome P450 from a baculovirus vector convert 4′,7-dihydroxyflavanone (liquiritigenin) to 4′,7-dihydroxyisoflavone (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-Hydroxyisoflavanone synthase transcripts are strongly induced in alfalfa cell suspensions in response to elicitation.