Metabolic engineering of narrow-leafed lupin for the production of enantiomerically pure (−)-sparteine

Abstract

The protein crops known as lupins have been bred to accumulate low levels of antinutritional alkaloids, neglecting their potential as sources of valuable metabolites. Here, we engineered narrow-leafed lupin (NLL) to accumulate large amounts of a single alkaloid of industrial interest called (−)-sparteine. While (−)-sparteine is recognized as a key auxiliary molecule in chiral synthesis, its variable price and limited availability have prevented its large-scale use. We identified two enzymes that initiate the conversion of (−)-sparteine to a variety of alkaloids accumulating in NLL. The first one is a cytochrome P450 monooxygenase belonging to family 71 (CYP71D189), and the second one is a short-chain dehydrogenase/reductase (SDR1). We screened a non-GMO NLL mutant library and isolated a knockout in CYP71D189. The knockout displayed an altered metabolic profile where (−)-sparteine accounted for 96% of the alkaloid content in the seeds (GC–MS basis). The (−)-sparteine isolated from the mutant seeds was enantiomerically pure (99% enantiomeric excess). Apart from the altered alkaloid profile, the mutant did not have any noticeable phenotype. Our work demonstrates that (−)-sparteine is the precursor of most QAs in NLL and expands the current uses of NLL as a crop.