# Discovery and Biosynthesis of Farnesyl Pyrophosphate-Derived Noncanonical C17 Terpenes from Pseudomonas Species

## TL;DR

This paper discovers a new C17 terpene from Pseudomonas and reveals how its biosynthesis can be manipulated for biotech applications.

## Contribution

Identification of a novel C17 terpene and functional characterization of enzymes that enhance its biosynthesis.

## Key findings

- Grimophan, a C17 terpene with a rare deltacyclane skeleton, was discovered from Pseudomonas grimontii.
- Methyltransferase-like enzymes enhance the production of noncanonical terpenes without performing group transfer.
- Modifying the terpene synthase PgrE altered product selectivity, enabling alternative terpene structures.

## Abstract

Terpenes make up
a structurally and functionally highly
diverse
class of natural products found across all living organisms. Pseudomonas species possess significant potential for the
biosynthetic assembly of farnesyl pyrophosphate (FPP)-derived terpenes
with unusual carbon skeletons. However, their structural and biosynthetic
diversity has been largely unexplored. Here, we report the discovery
of grimophan, a C17 terpene featuring a rare deltacyclane
skeleton. The compound was accessed by heterologous expression of
the pgr biosynthetic gene cluster from Pseudomonas grimontii DSM 17515 in E. coli. The roles of the enzymes involved in grimophan
biosynthesis were elucidated through in vitro reconstitution
of the entire biosynthetic pathway. In-depth functional studies on
the involved SAM-dependent methyltransferases led to the discovery
of methyltransferase-like enzymes that do not perform functional group
transfer, but rather significantly enhance the production titer of
noncanonical terpenes. These enzymes thus constitute valuable tools
for enhancing biotechnological production levels of noncanonical C16 and C17 terpenes. The function of the cognate
terpene synthase PgrE was evaluated by targeted point mutations within
the observed Asp-rich motif D92DMPLG97 to map
the effects of active-site residues on product formation. These investigations
facilitated redirecting product selectivity, leading to alternative
products. Overall, our work sheds light on the general biosynthetic
logic leading to noncanonical C17 terpenes and provides
a basis for their targeted discovery by genome mining and heterologous
expression and for engineering C17 terpene structural frameworks.