Abstract
Legumes show a pool of different triterpenoid saponins, however, most of their biosynthesis pathways are yet unknown. Previously, licorice (Glycyrriza spp.) β-amyrin 11-oxidase CYP88D6, which catalyzes the conversion of β-amyrin to 11-oxo-β-amyrin in the glycyrrhizin pathway, was identified using a yeast heterologous expression system. Similarly, CYP-A21 (tentative name) was identified as a second important P450 that is responsible for the oxidations at C-30 of 11-oxo-β-amyrin to produce glycyrrhetinic acid. In this work, using the Medicago truncatula EST database, 7 homologs of CYP-A21 and 2 homologs of CYP88D6 were identified and analyzed for their potential β-amyrin oxidizing activity using a yeast expression system. One of the CYP-A21 homologs (75%amino acid identity to CYP-A21) was able to catalyze three oxidation steps at C-30 of P450-amyrin to produce 11-deoxoglycyrrhetinic acid. Furthermore, when the activity of this CYP-A21 homolog was tested in combination with CYP88D6, GC-MS results showed their ability to produce glycyrrhetinic acid. The combination of various legume P450s are now in progress in order to generate new β-amyrin derivatives.