General base-general acid catalysis by terpenoid cyclases

Pemberton, T.A.; Christianson, D.W.

doi:10.1038/ja.2016.39

Cited by 21 publications

(29 citation statements)

References 65 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The water bound in the cavity created by substitution of Ala for this Ile would then similarly enable the effects on product outcome observed here with such I→A mutants of KSs ( Figures 3 and 4 ). In this mechanism the general base is most likely the pyrophosphate anion co-product, as previously suggested for class I terpene synthases in general (Pemberton and Christianson, 2016). …”

Section: Discussionmentioning

confidence: 52%

Extending a Single Residue Switch for Abbreviating Catalysis in Plant ent-Kaurene Synthases

Jia

Peters

2016

Front. Plant Sci.

View full text Add to dashboard Cite

Production of ent-kaurene as a precursor for important signaling molecules such as the gibberellins seems to have arisen early in plant evolution, with corresponding cyclase(s) present in all land plants (i.e., embryophyta). The relevant enzymes seem to represent fusion of the class II diterpene cyclase that produces the intermediate ent-copalyl diphosphate (ent-CPP) and the subsequently acting class I diterpene synthase that produces ent-kaurene, although the bifunctionality of the ancestral gene is only retained in certain early diverging plants, with gene duplication and sub-functionalization leading to distinct ent-CPP synthases and ent-kaurene synthases (KSs) generally observed. This evolutionary scenario implies that plant KSs should have conserved structural features uniquely required for production of ent-kaurene relative to related enzymes that have alternative function. Notably, substitution of threonine for a conserved isoleucine has been shown to “short-circuit” the complex bicyclization and rearrangement reaction catalyzed by KSs after initial cyclization, leading to predominant production of ent-pimaradiene, at least in KSs from angiosperms. Here this effect is shown to extend to KSs from earlier diverging plants (i.e., bryophytes), including a bifunctional/KS. In addition, attribution of the dramatic effect of this single residue “switch” on product outcome to electrostatic stabilization of the ent-pimarenyl carbocation intermediate formed upon initial cyclization by the hydroxyl introduced by threonine substitution has been called into question by the observation of similar effects from substitution of alanine. Here further mutational analysis and detailed product analysis is reported that supports the importance of electrostatic stabilization by a hydroxyl or water.

show abstract

Section: Discussionmentioning

confidence: 52%

Extending a Single Residue Switch for Abbreviating Catalysis in Plant ent-Kaurene Synthases

Jia

Peters

2016

Front. Plant Sci.

View full text Add to dashboard Cite

show abstract

“… 271 Additionally, the negative electrostatic potential of the inorganic pyrophosphate coproduct provides electrostatic stabilization of carbocation intermediates. Inorganic pyrophosphate may also serve widely as a general base to terminate the reaction sequence in class I terpenoid cyclization and coupling reactions, 3 , 75 , 80 and a water molecule may serve this function in class II terpenoid cyclases. 429 For class I or class II cyclases in which a water molecule adds to the final carbocation intermediate to terminate the reaction, the water molecule must be highly controlled so that it does not prematurely quench the sequence of carbocation intermediates in the cyclization cascade.…”

Section: Discussionmentioning

confidence: 99%

“…Since this water molecule is located near the geminal dimethyl group of 2-azabornane and (+)-bornyl diphosphate, which accordingly would be in the vicinity of the geminal dimethyl group of the α-terpinyl cation intermediate, it is possible that this water molecule hydroxylates the α-terpinyl cation in the cineole synthase mechanism. Given the likely role of coproduct inorganic pyrophosphate as a potential general base-general acid catalyst, 80 inorganic pyrophosphate may deprotonate this water molecule upon hydroxylation of the α-terpinyl cation and then protonate the carbon–carbon double bond of α-terpineol to enable cineole formation as shown in Figure 41 .…”

Section: Class I Terpenoid Cyclasesmentioning

confidence: 99%

See 1 more Smart Citation

Structural and Chemical Biology of Terpenoid Cyclases

2017

View full text Add to dashboard Cite

The year 2017 marks the twentieth anniversary of terpenoid cyclase structural biology: a trio of terpenoid cyclase structures reported together in 1997 were the first to set the foundation for understanding the enzymes largely responsible for the exquisite chemodiversity of more than 80000 terpenoid natural products. Terpenoid cyclases catalyze the most complex chemical reactions in biology, in that more than half of the substrate carbon atoms undergo changes in bonding and hybridization during a single enzyme-catalyzed cyclization reaction. The past two decades have witnessed structural, functional, and computational studies illuminating the modes of substrate activation that initiate the cyclization cascade, the management and manipulation of high-energy carbocation intermediates that propagate the cyclization cascade, and the chemical strategies that terminate the cyclization cascade. The role of the terpenoid cyclase as a template for catalysis is paramount to its function, and protein engineering can be used to reprogram the cyclization cascade to generate alternative and commercially important products. Here, I review key advances in terpenoid cyclase structural and chemical biology, focusing mainly on terpenoid cyclases and related prenyltransferases for which X-ray crystal structures have informed and advanced our understanding of enzyme structure and function.

show abstract

“…Indeed, the perceived lack of side chains with suitable basicity has led to the hypothesis that the pyrophosphate anion co-product ( -OPP) generally serves as the catalytic (general) base. 2 Previous work has demonstrated that single residue changes can switch product outcome in certain plant diterpene synthases. [3][4][5][6][7][8][9][10][11] Arguably the most interesting changes are those involving a key position that controls the complexity of the catalytic reaction.…”

mentioning

confidence: 99%

Switching on a Nontraditional Enzymatic Base—Deprotonation by Serine in the ent-Kaurene Synthase from Bradyrhizobium japonicum

et al. 2019

View full text Add to dashboard Cite

Terpene synthases often catalyze complex carbocation cascade reactions. It has been previously shown that single-residue switches involving replacement of a key aliphatic residue with serine or threonine can "shortcircuit" such reactions that are presumed to act indirectly via dipole stabilization of intermediate carbocations. Here a similar switch was found in the structurally characterized ent-kaurene synthase from Bradyrhizobium japonicum. Application of a recently developed computational approach to terpene synthases, TerDockin, surprisingly indicates direct action of the introduced serine hydroxyl as a catalytic base. Notably, this model suggests an alternative interpretation of previous results and potential routes toward reengineering terpene synthase activity more generally.

show abstract

General base-general acid catalysis by terpenoid cyclases

Cited by 21 publications

References 65 publications

Extending a Single Residue Switch for Abbreviating Catalysis in Plant ent-Kaurene Synthases

Extending a Single Residue Switch for Abbreviating Catalysis in Plant ent-Kaurene Synthases

Structural and Chemical Biology of Terpenoid Cyclases

Switching on a Nontraditional Enzymatic Base—Deprotonation by Serine in the ent-Kaurene Synthase from Bradyrhizobium japonicum

Contact Info

Product

Resources

About