Discovery and biosynthesis of non-canonical C16-terpenoids from Pseudomonas

Abstract

Biosynthesis of sodorifen with a unique C₁₆-bicyclo[3.2.1]octene framework requires an S-adenosyl methionine-dependent methyltransferase SodC and terpene cyclase SodD. While bioinformatic analyses reveal a wide distribution of the sodCD genes organization in bacteria, their functional diversity remains largely unknown. Herein, two sodorifen-type gene clusters, pcch and pcau, from Pseudomonas sp. are heterologously expressed in Escherichia coli, leading to the discovery of two C₁₆ terpenoids. Enzymatic synthesis of these compounds is achieved using the two (SodCD-like) pathway-specific enzymes. Enzyme assays using different combinations of methyltransferases and terpene synthases across the pcch, pcau, and sod pathways reveal a unifying biosynthetic mechanism: all three SodC-like enzymes methylate farnesyl pyrophosphate (FPP) with subsequent cyclization to a common intermediate, pre-sodorifen pyrophosphate. Structural diversification of this joint precursor solely occurs by the subsequently acting individual terpene synthases. Our findings expand basic biosynthetic understanding and structural diversity of unusual C₁₆-terpenoids.

Keywords: C(16) terpenoids; Pseudomonas species; aristotelene; direct pathway cloning, DiPaC; enzymatic synthesis; heterologous expression; non-canonical terpenoids; pathway reconstitution; pseudorifen; volatile bacterial metabolites.