Identification of a pentaketide stilbene produced by a type III polyketide synthase from Pinus sylvestris and characterisation of free coenzyme A intermediates.

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.