Astertarone A Synthase from Chinese Cabbage Does Not Produce the C4-Epimer: Mechanistic Insights

Org Lett. 2018 Apr 6;20(7):1802-1805. doi: 10.1021/acs.orglett.8b00302. Epub 2018 Mar 20.

Abstract

The Brassica rapa oxidosqualene cyclase Bra032185 makes 60% astertarone A (1) and 20 minor triterpenes (0.1-11%). Mechanistic analysis indicates the absence of an enol intermediate to generate the 4 S epimer of 1, unless workup involves saponification. Bra032185 and its closest Arabidopsis thaliana homologue diverged markedly in product profiles over a short evolutionary distance, while developing opposite C18 configurations. Active-site residue comparison of Bra032185 with friedelin and shionone synthases suggests convergent evolution to 3-ketotriterpenes.

Publication types

  • Research Support, Non-U.S. Gov't