Total biosynthesis of the cyclic AMP booster forskolin from Coleus forskohlii

Abstract

Forskolin is a unique structurally complex labdane-type diterpenoid used in the treatment of glaucoma and heart failure based on its activity as a cyclic AMP booster. Commercial production of forskolin relies exclusively on extraction from its only known natural source, the plant <i>Coleus forskohlii</i>, in which forskolin accumulates in the root cork. Here, we report the discovery of five cytochrome P450s and two acetyltransferases which catalyze a cascade of reactions converting the forskolin precursor 13<i>R</i>-manoyl oxide into forskolin and a diverse array of additional labdane-type diterpenoids. A minimal set of three P450s in combination with a single acetyl transferase was identified that catalyzes the conversion of 13<i>R</i>-manoyl oxide into forskolin as demonstrated by transient expression in <i>Nicotiana benthamiana</i>. The entire pathway for forskolin production from glucose encompassing expression of nine genes was stably integrated into <i>Saccharomyces cerevisiae</i> and afforded forskolin titers of 40 mg/L.