Discovery of a cytochrome P450 enzyme catalyzing the formation of spirooxindole alkaloid scaffold

Abstract

Spirooxindole alkaloids feature a unique scaffold of an oxindole ring sharing an atom with a heterocyclic moiety. These compounds display an extensive range of biological activities such as anticancer, antibiotics, and anti-hypertension. Despite their structural and functional significance, the establishment and rationale of the spirooxindole scaffold biosynthesis are yet to be elucidated. Herein, we report the discovery and characterization of a cytochrome P450 enzyme from kratom (<i>Mitragyna speciosa</i>) responsible for the formation of the spirooxindole alkaloids 3-<i>epi</i>-corynoxeine (3<i>R</i>, 7<i>R</i>) and isocorynoxeine (3<i>S</i>, 7<i>S</i>) from the corynanthe-type (3<i>R</i>)-secoyohimbane precursors. Expression of the newly discovered enzyme in <i>Saccharomyces cerevisiae</i> yeast allows for the efficient <i>in vivo</i> and <i>in vitro</i> production of spirooxindoles. This discovery highlights the versatility of plant cytochrome P450 enzymes in building unusual alkaloid scaffolds and opens a gateway to access the prestigious spirooxindole pharmacophore and its derivatives.