Engineered Microbes for Producing Anticholinergics

Abstract

The tropane alkaloids (TAs) hyoscyamine and scopolamine function as acetylcholine receptor antagonists and are used clinically as parasympatholytics to treat neuromuscular disorders in humans. While TAs are synthesized in a small subset of plant families, these specialized metabolites are only accumulated in limited quantities in plant organs. The complex chemical structures of these compounds make their industrial production by chemical synthesis very challenging, Therefore, the supply of these TAs still relies on intensive farming of Duboisia shrubs in tropical countries. Many adverse factors such as climate fluctuations and pandemics can thus influence annual world production. Based on the landmark microbial production of the antimalarial semi‐synthetic artemisinin, the Smolke group recently developed a yeast cell factory capable of de novo synthesizing hyoscyamine and scopolamine, thus paving the way for an alternative production of these compounds.

Optimization of Tabersonine Methoxylation to Increase Vindoline Precursor Synthesis in Yeast Cell Factories

“…Therefore, the tight control of the metabolic flux in yeast constitutes a main concern for an optimal production of vindoline through tabersonine bioconversion with reduced accumulation of intermediates and limited vindorosine synthesis. A similar rationale has been already pointed out for benzylisoquinoline [29][30][31][32] and tetrahydroisoquinoline [33,34] alkaloids.…”

“…Promoting specialized metabolite synthesis in yeast can be achieved through the selection and expression of the most active orthologues of enzymes displaying low activity. A nice example of this strategy was recently described for phenylpyruvate reductase to optimize the synthesis of tropane alkaloids in heterologous hosts [31,32]. We thus took advantage of the recently published orthologue of 16OMT from Vinca Minor (Vm16OMT) and measured its 16-hydroxytabersonine methylation activity in yeast [54].…”

“…Among the potential heterologous hosts, yeast is considered as one of the most suitable organisms for metabolic engineering due to its fast growth, easy genetic manipulation, and available genome sequence [22]. Following the seminal heterologous productions of artemisinin [23], hydrocortisone [24], and progesterone [25], several plant alkaloids have been more recently biosynthesized by recombinant yeast, such as MIAs [26][27][28] but also benzylisoquinoline [29][30][31][32] and tetrahydroisoquinoline [33,34] alkaloids. However, heterologous biosynthesis of MIAs remains challenging due to the high complexity of the pathway and the elaborate cellular and subcellular compartmentalization of enzymes [35][36][37].…”