A new 3,6-dialkyl--pyrone produced by the heterologous expression of a PKS-NRPS hybrid enzyme derived from a Pestalotiopsis endophyte

Genome mining of polyketide synthase (PKS)-nonribosomal peptide synthetase (NRPS) hybrid enzymes independent of trans-acting enoyl reductase using our in-house fungal draft genomic library led to the discovery of a unique PKS-NRPS hybrid enzyme, PbpsA, in a Pestalotiopsis fungus. Heterologously expressed PbpsA in Aspergillus oryzae provided a new 3,6-dialkyl-alpha-pyrone 1. This compound was fully characterized following the interpretation of NMR, UV, IR, and MS data. From the structure, we speculated that 1 was biosynthesized by the only PKS moiety of PbpsA, and that a 3-ethyl substitution was introduced by an endogenous enzyme from A. oryzae.