Alternative splicing-induced thioesterase domain deficiency drives the production of natural orsellinic acid derivatives with a pantetheine moiety in nonreducing polyketide synthases.

Nonreducing polyketide synthase Preu6 catalyzes didepside formation by interaction of starter acyl transferase and thioesterase (TE) domains. Here, we show that an aberrant transcript, preu6β, is generated to encode the TE-deficient protein via alternative splicing in A5SS pattern. Upon heterologous expression in Saccharomyces cerevisiae BJ5464-NpgA, coupled with in vitro chemical and enzymatic assays, Preu6β affords compound 9, the first natural orsellinic acid (OA) derivative with a pantetheine (PANT) moiety. We also demonstrate that TE inactivation represents a previously unrecognized mechanism that governs the selective formation of OA derived-PANT products.