Cross-reaction of chalcone synthase and stilbene synthase overexpressed inEscherichia coli

Chalcone synthase (CHS) and stilbene synthase (STS) are related plant polyk etide synthases belonging to the CHS superfamily. CHS and STS catalyze comm on condensation reactions of p-coumaroyl-CoA and three C-2-units from malon yl-CoA but different cyclization reactions to produce naringenin chalcone a nd resveratrol, respectively. Using purified Pueraria lobata CHS and Arachi s hypogaea STS overexpressed in Escherichia coli, bisnoryangonin (BNY, the derailed lactone after two condensations) and p-coumaroyltriacetic acid lac tone (thr derailed lactone after three condensations) mere detected from th e reaction products. More importantly, we found a crossreaction between CHS and STS, i.e. resveratrol production by CHS (2.7-4.2% of naringenin) and n aringenin production by STS (1.4-2.3% of resveratrol), possibly due to the conformational flexibility of their active sites. (C) 1999 Federation of Eu ropean Biochemical Societies.