Identification of a Pentaketide Stilbene Produced by a Type III Polyketide Synthase from Pinus sylvestris and Characterisation of Free Coenzyme A Intermediates

By miscounting the number of malonyl‐CoA condensations, the stilbene synthase (STS) from Pinus sylvestris forms the previously unknown pentaketide, 2‐malonylresveratrol, in addition to the expected tetraketide resveratrol (see scheme). This is the first time that such tetra‐ and pentaketide‐CoA derivatives have been observed; this suggests that these products might be free intermediates in the biosynthesis of stilbenes. magnified image The stilbene synthase (STS) from Scots pine ( Pinus sylvestris ), which is a type III polyketide synthase, produces the well known tetraketide resveratrol from coumaroyl‐CoA and three molecules of malonyl‐CoA. The same stilbene synthase, however, also generates the previously unknown pentaketide 2‐malonylresveratrol from coumaroyl‐CoA and four molecules of malonyl‐CoA; this indicates that the enzyme does not precisely control the number of condensations leading to diverse products. Tetraketide‐ and pentaketide‐CoA intermediates of the STS were identified by LC‐MS/MS; this suggests that CoA‐bound polyketide intermediates are involved in the product formation of type III polyketide synthases.