1. Astertarone A Synthase from Chinese Cabbage Does Not Produce the C4-Epimer: Mechanistic Insights
- Author
-
William K. Wilson, Jing Jin, Megan K. Moore, and Seiichi P. T. Matsuda
- Subjects
ATP synthase ,biology ,010405 organic chemistry ,Stereochemistry ,Organic Chemistry ,Friedelin ,010402 general chemistry ,biology.organism_classification ,01 natural sciences ,Biochemistry ,Enol ,0104 chemical sciences ,Terpene ,chemistry.chemical_compound ,Residue (chemistry) ,chemistry ,Brassica rapa ,biology.protein ,Arabidopsis thaliana ,Epimer ,Physical and Theoretical Chemistry - 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.
- Published
- 2018