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A chemically programmed proximal ligand enhances the catalytic properties of a heme enzyme


Green, Anthony P; Hayashi, Takahiro; Mittl, Peer R E; Hilvert, Donald (2016). A chemically programmed proximal ligand enhances the catalytic properties of a heme enzyme. Journal of the American Chemical Society, 138(35):11344-11352.

Abstract

Enzymes rely on complex interactions between precisely positioned active site residues as a mechanism to compensate for the limited functionality contained within the genetic code. Heme enzymes provide a striking example of this complexity, whereby the electronic properties of reactive ferryl intermediates are finely tuned through hydrogen bonding interactions between proximal ligands and neighboring amino acids. Here, we show that introduction of a chemically programmed proximal Nδ-methyl histidine (NMH) ligand into an engineered ascorbate peroxidase (APX2) overcomes the reliance on the conserved Asp-His hydrogen bonding interaction, leading to a catalytically modified enzyme (APX2 NMH), which is able to achieve a significantly higher number of turnovers compared with APX2 without compromising catalytic efficiency. Structural, spectroscopic and kinetic characterization of APX2 NMH and several active site variants provides valuable insights into the role of the Asp-His-Fe triad of heme peroxidases. More significantly, simplification of catalytic mechanisms through the incorporation of chemically optimized ligands may facilitate efforts to create and evolve new active site heme environments within proteins.

Abstract

Enzymes rely on complex interactions between precisely positioned active site residues as a mechanism to compensate for the limited functionality contained within the genetic code. Heme enzymes provide a striking example of this complexity, whereby the electronic properties of reactive ferryl intermediates are finely tuned through hydrogen bonding interactions between proximal ligands and neighboring amino acids. Here, we show that introduction of a chemically programmed proximal Nδ-methyl histidine (NMH) ligand into an engineered ascorbate peroxidase (APX2) overcomes the reliance on the conserved Asp-His hydrogen bonding interaction, leading to a catalytically modified enzyme (APX2 NMH), which is able to achieve a significantly higher number of turnovers compared with APX2 without compromising catalytic efficiency. Structural, spectroscopic and kinetic characterization of APX2 NMH and several active site variants provides valuable insights into the role of the Asp-His-Fe triad of heme peroxidases. More significantly, simplification of catalytic mechanisms through the incorporation of chemically optimized ligands may facilitate efforts to create and evolve new active site heme environments within proteins.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Department of Biochemistry
07 Faculty of Science > Department of Biochemistry
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:7 September 2016
Deposited On:17 Oct 2016 09:05
Last Modified:17 Oct 2016 09:05
Publisher:American Chemical Society (ACS)
ISSN:0002-7863
Publisher DOI:https://doi.org/10.1021/jacs.6b07029
PubMed ID:27500802

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