Campus Units

Biochemistry, Biophysics and Molecular Biology

Document Type

Article

Publication Version

Published Version

Publication Date

7-2-2010

Journal or Book Title

Journal of Biological Chemistry

Volume

285

Issue

27

First Page

20558

Last Page

20563

DOI

10.1074/jbc.M110.123307

Abstract

Class II diterpene cyclases mediate the acid-initiated cycloisomerization reaction that serves as the committed step in biosynthesis of the large class of labdane-related diterpenoid natural products, which includes the important gibberellin plant hormones. Intriguingly, these enzymes are differentially susceptible to inhibition by their Mg2+ cofactor, with those involved in gibberellin biosynthesis being more sensitive to such inhibition than those devoted to secondary metabolism, which presumably limits flux toward the potent gibberellin phytohormones. Such inhibition has been suggested to arise from intrasteric Mg2+ binding to the DXDD motif that cooperatively acts as the catalytic acid, whose affinity must then be modulated in some fashion. While further investigating class II diterpene cyclase catalysis, we discovered a conserved basic residue that seems to act as a counter ion to the DXDD motif, enhancing the ability of aspartic acid to carry out the requisite energetically difficult protonation of a carbon-carbon double bond and also affecting inhibitory Mg2+binding. Notably, this residue is conserved as a histidine in enzymes involved in gibberellin biosynthesis and as an arginine in those dedicated to secondary metabolism. Interchanging the identity of these residues is sufficient to switch the sensitivity of the parent enzyme to inhibition by Mg2+. These striking findings indicate that this is a single residue switch for Mg2+ inhibition, which not only supports the importance of this biochemical regulatory mechanism in limiting gibberellin biosynthesis, but the importance of its release, presumably to enable higher flux, into secondary metabolism.

Comments

This research was originally published in Journal of Biological Chemistry. Mann FM, Prisic S, Davenport EK, Determan MK, Coates RM, Peters RJ. A single residue switch for Mg2+-dependent inhibition characterizes plant class II diterpene cyclases from primary and secondary metabolism. Journal of Biological Chemistry. 2010 Jul 2;285:20558-63. © the American Society for Biochemistry and Molecular Biology.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Copyright Owner

The American Society for Biochemistry and Molecular Biology, Inc.

Language

en

File Format

application/pdf

Share

COinS