Cytochrome P450 CYP716A254 catalyzes the formation of oleanolic acid from β-amyrin during oleanane-type triterpenoid saponins biosynthesis in Anemone flaccida

Abstract

Anemone flaccida Fr. Shmidt (Ranunculaceae), known as 'Di Wu' in China, is a perennial herb which has long been used to treat arthritis. The rhizome of A. flaccida contains pharmacologically active components i.e. oleanane-type triterpenoid saponins. Oleanolic acid is natural triterpenoid in plants with diverse biological activities. The biosynthesis of oleanolic acid involves cyclization of 2,3-oxidosqualene to the oleanane-type triterpenoid skeleton, followed by a series of oxidation reactions catalyzed by cytochrome P450 monooxygenase (CYP450). Previously, we identified four possible cytochrome P450 genes belonging to CYP716A subfamily from the transcriptome of A. flaccida. In this study, we identified one of those genes "CYP716A254" encoding a cytochrome P450 monooxygenase from A. flaccida that catalyzes the conversion of the β-amyrin into oleanolic acid. The heterologous expression of CYP716A254 in yeast resulted in oxidation of β-amyrin at the C-18 position to oleanolic acid production. These results provide an important basis for further studies of oleanane-type triterpenoid saponins synthesis in A. flaccida.

Keywords: Anemone flaccida; CYP716A254; Cytochrome P450; Oleanolic acid; β-Amyrin.