Local charge distributions, electric dipole moments and local electric fields influence reactivity patterns and guide regioselectivities in α-ketoglutarate-dependent nonheme iron dioxygenases.

Sam P. De Visser, Gourab Mukherjee, Hafiz Saqib Ali, Chivukula V Sastri

Research output: Contribution to journalArticlepeer-review


Nonheme iron dioxygenases catalyze vital processes for human health related to the biosynthesis of essential products and the biodegradation of toxic metabolites. Often the natural product biosynthesis by these nonheme iron dioxygenases is highly regio- and chemoselective, which are commonly assigned to tight substrate binding and positioning. However, recent highlevel computational modeling has shown that substrate binding and positioning is only part of the story and long-range electrostatic interactions can play a major additional role. In this Account, we review and summarize computational viewpoints on the high regioand chemoselectivity of α-ketoglutarate-dependent nonheme iron dioxygenases and how external perturbations affect the catalysis.
In particular, studies from our groups have shown that often a regioselectivity in enzymes can be accomplished by external perturbations working on the transition state for the reaction through external charges, electric dipole moments or local electric field effects.
Furthermore, bond dissociation energies in molecules are shown to be influenced by an electric field effect; and through targeting a specific bond in an electric field this can lead to an unusual specificity reaction. For instance, in the carbon-induced starvation protein, we studied two substrate-bound conformations and showed that regardless of what C-H bond of the substrate is closest to the iron(IV)-oxo oxidant, the lowest hydrogen atom abstraction barrier is always for the pro-S C²-H abstraction due to an induced dipole moment of the protein that weakens this bond. In another example on the hygromycin biosynthesis enzyme, an oxidative ring-closure reaction
in the substrate forms an ortho-δ-ester ring. Calculations on this enzyme show that the selectivity is guided by a protonated lysine residue in the active site that, through its positive charge, triggers a low energy hydrogen atom abstraction barrier. A final set of examples in this Account discuss the viomycin biosynthesis enzyme and the 2-(trimethylammonio)ethylphosphonate dioxygenase (TmpA) enzymes. Both of these enzymes are shown to possess a significant local electric dipole moment and local electric field effect due to charged residues surrounding the substrate and oxidant binding pocket. This dipole moment and local electric field strength
changes the C-H bond strengths of the substrate and triggers the regioselectivity of substrate activation. In particular, we show that in the gas-phase and in an enzyme environment C-H bond strengths vary due to local electric dipole moments and electric field strengths. These examples show that enzymes have an intricately designed structure that enables a chemical reaction under ambient conditions through the positioning of positively and negatively charged residues that influence and enhance reaction mechanisms. These computational insights create huge possibilities in bioengineering to apply local electric field and dipoles in proteins to achieve an unusual reaction selectivity and trigger a fit-for-purpose biocatalyst for unique biotransformations.
Original languageEnglish
JournalAccounts of Chemical Research
Publication statusAccepted/In press - 2 Dec 2021

Research Beacons, Institutes and Platforms

  • Manchester Institute of Biotechnology


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