Enzymatic Formation of an Unnatural C<INF>6</INF>−C<INF>5</INF> Aromatic Polyketide by Plant Type III Polyketide Synthases

<UFIGR ID="ol0201409n00001">Substrate specificities of plant polyketide synthases (PKSs) were investigated using analogues of malonyl-CoA, the extension unit of the polyketide chain elongation reactions. When incubated with methylmalonyl-CoA and 4-coumaroyl-CoA, plant PKSs (chalcone synthase from Scutellaria baicalensis, stilbene synthase from Arachis hypogaea, and benzalacetone synthase from Rheum palmatum) afforded an unnatural C<INF>6</INF>−C<INF>5</INF> aromatic polyketide, 1-(4-hydroxyphenyl)pent-1-en-3-one, formed by one-step decarboxylative condensation of the two substrates. In contrast, succinyl-CoA was not accepted as a substrate by the enzymes.