Discovery of sarpagan bridge enzyme-mediated pericyclivine biosynthesis
University of New Brunswick
Sarpagan Bridge Enzymes (SBEs) are cytochrome P450 monooxygenases catalyzing the coupling reaction of C5-C16 sarpagan bridge in the biosynthesis of many sarpagan type monoterpenoid indole alkaloids. This includes the anti-arrhythmic drug ajmaline in Rauwolfia serpentina from the Apocynaceae plant family. Despite SBE enzymatic activity first being detected over 20 years ago, only a handful of these enzymes have been identified and characterized. Here, we report the discovery and characterization of two new SBEs in the plants Catharanthus roseus and Tabernaemontana elegans. Through virus-induced gene silencing and a series of in vivo and in vitro assays, we confirmed these enzymes catalyze the cyclization and aromatization reactions characteristic to SBEs. Furthermore, the addition of C. roseus and T. elegans leaf total proteins to in vitro assays confirmed these SBEs’ involvement in pericyclivine biosynthesis. The discovery of these two enzymes continues to expand our knowledge on the pathways SBEs are found in and adds another step in the complete elucidation of perivine and vobasine biosynthetic pathways.