Engineering Saccharomyces Cerevisiae for Monoterpene Bioconversion By Modulating α,β-Unsaturated Aldehyde Metabolism.

Monoterpene indole alkaloids (MIAs) represent a structurally diverse, medicinally essential class of plant derived natural products. Catharanthus roseus is a prolific producer of MIAs, as well as the source of the indispensable chemotherapeutic MIAs vinblastine and vincristine. A key enzymatic step in MIA biosynthesis involves the non-canonical, reductive cyclization of the monoterpene 8-oxogeranial by iridoid synthase to form nepetalactol. Generation of a bicyclic molecule with four chiral centers, from a precursor that is both acyclic and achiral demonstrates that Mother Nature is truly the best synthetic chemist. In the process of leveraging a bioconversion production strategy in Saccharomyces cerevisiae, we have identified 8-oxogeranial as the primary pathway intermediate from which a number of shunt products are derived. By modulating yeast’s metabolism of 8-oxogeranial, which contains two α,β-unsaturated aldehydes, we illustrate the roles played by several key enzymes in disrupting the heterologous production of nepetalactol. Furthermore, we clarify confusion in the field regarding reduction of pathway intermediates in yeast by endogenous and exogenous enzymes. We anticipate that our engineered platform will play an important role in development of S. cerevisiae for production of iridoids and MIAs.