Campus Units

Biochemistry, Biophysics and Molecular Biology

Document Type

Article

Publication Version

Accepted Manuscript

Publication Date

9-1-2013

Journal or Book Title

Biochemical Journal

Volume

454

Issue

2

First Page

209

Last Page

216

DOI

10.1042/BJ20130574

Abstract

Natural products biosynthesis often requires the action of multiple cytochromes P450 (CYPs), whose ability to introduce oxygen, increasing solubility, is critical for imparting biological activity. In previous investigations of rice diterpenoid biosynthesis, we have characterized CYPs that catalyze alternative hydroxylation of ent-sandaracopimaradiene, the precursor to the rice oryzalexin antibiotic phytoalexins. In particular, CYP76M5, -6 and -8 were all shown to carry out C7β-hydroxylation, while CYP701A8 catalyzes C3α-hydroxylation, with oxy groups found at both positions in oryzalexins A–D, suggesting that these may act consecutively in oryzalexin biosynthesis. Here we report that, although CYP701A8 only poorly reacts with 7β-hydroxy-entsandaracopimaradiene, CYP76M6 and -8 readily react with 3α-hydroxy-entsandaracopimaradiene. Notably, their activity yields distinct products, resulting from hydroxylation at C9β by CYP76M6 or C7β by CYP76M8, on different sides of the core tricyclic ring structure. Thus, CYP76M6 and -8 have distinct, non-redundant roles in orzyalexin biosynthesis. Moreover, the resulting 3α,7β- and 3α,9β- diols correspond to oryzalexins D and E, respectively. Accordingly, our results complete the functional identification of the biosynthetic pathway underlying the production of these bioactive phytoalexins. In addition, the altered regiochemistry catalyzed by CYP76M6 following C3α-hydroxylation has some implications for its active site configuration, offering further molecular insight.

Comments

This is a pre-publication manuscript of an article published as Picking sides: distinct roles for CYP76M6 and CYP76M8 in rice oryzalexin biosynthesis, Yisheng Wu, Qiang Wang, Matthew L. Hillwig, Reuben J. Peters, Biochemical Journal, Sep 2013, 454(2)209-216; DOI: 10.1042/BJ20130574. Posted with permission.

Copyright Owner

The Authors

Language

en

File Format

application/pdf

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