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

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 4S epimer of 1, unless workup involves saponification. Bra032185 and its closest Arabidopsis thaliana h...

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Bibliographic Details
Published in:Organic letters 2018-04, Vol.20 (7), p.1802-1805
Main Authors: Jin, Jing, Moore, Megan K, Wilson, William K, Matsuda, Seiichi P. T
Format: Article
Language:English
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Summary: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 4S 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.
ISSN:1523-7060
1523-7052
DOI:10.1021/acs.orglett.8b00302