β-Amyrin synthase (EsBAS) and 13-amyrin 28-oxidase (CYP716A244) in oleanane-type triterpene saponin biosynthesis in Eleutherococcus senticosus

Siberian ginseng (Eleutherococcus senticosus) is a woody medical shrub belonging to the Araliaceae family. E. senticosus contains various types of saponins, including oleanane, noroleanane, lupane, and 3,4-secolupane types, depending on the aglycone structure. Oleanane-type triterpenes are the major saponin components in E. senticosus. Two enzymes (beta-amyrin synthase and (beta-amyrin 28-oxidase) are essential for oleanane-type saponin biosynthesis from 2,3-oxidosqualene. In the present study, two full-length cDNAs encoding EsBAS and CYP716A244 were isolated based on transcriptomics analysis of plant leaves. Both beta-amyrin synthase (EsBAS) and beta-amyrin 28-oxidase (CYP716A244), isolated from E. senticosus, were functionally characterised. beta-amyrin production was confirmed by heterologous expression of the EsBAS gene in yeast and tobacco. Oleanolic acid production was confirmed by co-expression of both EsBAS and CYP716A244 in engineered yeast and transgenic tobacco. (C) 2016 Elsevier Ltd. All rights reserved.