Product identification of non-reducing polyketide synthases with C-terminus methyltransferase domain from Talaromyces stipitatus using Aspergillus oryzae heterologous expression

Abstract Talaromyces stipitatus ATCC 10500 possesses 17 non-reducing polyketide synthase (NR-PKS) genes. During the course of our functional analysis of PKS genes with a C-terminus methyltransferase domain from T. stipitatus , we expressed tspks2 , tspks3 and tspks4 genes in the heterologous host Aspergillus oryzae , respectively. Although the tspks4 transformant gave no apparent product in HPLC analysis, a novel azaphilone pentaketide ( 3 ) was identified along with two known related products from the tspks2 transformant. Of four hexaketide products from the tspks3 transformant, two new compounds were identified to be 2-acetyl-7-methyl-3,6,8-trihydroxynaphthalene ( 4 ) and its derivative fused with α-methyl-α,β-unsaturated γ-lactone ( 7 ).