Two bi-functional cytochrome P450 CYP72 enzymes from olive (Olea europaea) catalyze the oxidative C-C bond cleavage in the biosynthesis of secoxy-iridoids - flavor and quality determinants in olive oil

Olive (Olea europaea) is an important crop in Europe, with a particular agricultural and economic relevance in the Mediterranean area. The nutritional significance of olive fruits and oil is widely recognized. Olive oil flavor and quality depend on phenolic secoiridoids, whose biosynthetic pathway is just beginning to be understood. We report the characterization of two bifunctional cytochrome P450 enzymes, catalyzing the rare oxidative C-C bond cleavage of 7-epi-loganin to produce oleoside methyl ester (gene OeOMES) and secoxyloganin (gene OeSXS), both through a ketologanin intermediary. The reported enzymes are homologous to the known Catharanthus roseus secologanin synthase (CrSLS) but their substrate and product profiles differ. Biochemical assays and model-guided mutations allowed insights into the molecular basis and mechanism of the reactions. Notably the results suggest that, in contrast to published hypotheses, in planta production of secoxy-iridoids is secologanin-independent. Genomic analysis of cultivated and wild olives suggest a relation between domestication and OeOMES expression, this relevant result has the potential to enable development of genetic markers to guide next-generation breeding programs.