The assembly of (+)-vincadifformine and (-)-tabersonine derived monoterpenoid indole alkaloids in Catharanthus roseus involve separate branch pathways.

The biological activity of monoterpenoid indole alkaloids (MIAs) has led to discoveries for their use in cancer treatments and other medical applications. Their biosynthesis has involved formation of reactive intermediates used by responsible enzymes to elaborate several different chemical scaffolds. Modification of scaffolds through different substitution reactions has produced chemically diverse MIAs and related biological activities. The present study characterizes the 3-step pathway involved in the formation of (+)-echitovenine, the major O-acetylated MIA of Catharanthus roseus roots and differentiates it from a parallel pathway involved in the formation of hörhammericine. Separate hydrolases convert a common reactive MIA intermediate to aspidosperma skeletons of opposite specific rotations, i.e. (+)-vincadifformine and (-)-tabersonine, respectively. The formation of (+)-echitovenine from (+)-vincadifformine involves (+)-vincadifformine 19-hydroxylase (V19H), a root-specific cytochrome P450 with high amino acid sequence similarity to the tabersonine-3-oxygenase (T3O; CYP71D1V1) involved in vindoline biosynthesis in C. roseus leaves and minovincinine-O-acetyltransferase (MAT). The substrate specificity of V19H and MAT for their respective (+)-enantiomers defines the separate enantiomer-specific pathway involved in (+)-echitovenine biosynthesis and differentiates it from a parallel (-)-enantiomer specific pathway involved in the formation of hörhammericine from (-)-tabersonine. This article is protected by copyright. All rights reserved.