18O kinetic isotope effects in non-heme iron enzymes: Probing the nature of Fe/O2 intermediates

Liviu M. Mirica; Kevin P. McCusker; Jeffrey W. Munos; Hung Wen Liu; Judith P. Klinman

doi:10.1021/ja800265s

¹⁸O kinetic isotope effects in non-heme iron enzymes: Probing the nature of Fe/O₂ intermediates

Liviu M. Mirica, Kevin P. McCusker, Jeffrey W. Munos, Hung Wen Liu, Judith P. Klinman

Research output: Contribution to journal › Article › peer-review

Abstract

Contrasted here are the competitive ¹⁸O/¹⁶O kinetic isotope effects (¹⁸O KIEs) on k_cat/K_m(O₂) for three non-heme iron enzymes that activate O₂ at an iron center coordinated by a 2-His-1-carboxylate facial triad: taurine dioxygenase (TauD), (S)-(2)-hydroxypropylphosphonic acid epoxidase (HppE), and 1-aminocyclopropyl-1-carboxylic acid oxidase (ACCO). Measured ¹⁸O KIEs of 1.0102 ± 0.0002 (TauD), 1.0120 ± 0.0002 (HppE), and 1.0215 ± 0.0005 (ACCO) suggest the formation in the rate-limiting step of O₂ activation of an Fe^III-peroxohemiketal, Fe^III-OOH, and Fe^IV=O species, respectively. The comparison of the measured ¹⁸O KIEs with calculated or experimental ¹⁸O equilibrium isotope effects (¹⁸O EIEs) provides new insights into the O₂ activation through an inner-sphere mechanism at a non-heme iron center.

Original language	English (US)
Pages (from-to)	8122-8123
Number of pages	2
Journal	Journal of the American Chemical Society
Volume	130
Issue number	26
DOIs	https://doi.org/10.1021/ja800265s
State	Published - Jul 2 2008
Externally published	Yes

ASJC Scopus subject areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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10.1021/ja800265s

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@article{bd8427d2feda490fa80074fa87b5aac4,

title = "18O kinetic isotope effects in non-heme iron enzymes: Probing the nature of Fe/O2 intermediates",

abstract = "Contrasted here are the competitive 18O/16O kinetic isotope effects (18O KIEs) on kcat/Km(O2) for three non-heme iron enzymes that activate O2 at an iron center coordinated by a 2-His-1-carboxylate facial triad: taurine dioxygenase (TauD), (S)-(2)-hydroxypropylphosphonic acid epoxidase (HppE), and 1-aminocyclopropyl-1-carboxylic acid oxidase (ACCO). Measured 18O KIEs of 1.0102 ± 0.0002 (TauD), 1.0120 ± 0.0002 (HppE), and 1.0215 ± 0.0005 (ACCO) suggest the formation in the rate-limiting step of O2 activation of an FeIII-peroxohemiketal, FeIII-OOH, and FeIV=O species, respectively. The comparison of the measured 18O KIEs with calculated or experimental 18O equilibrium isotope effects (18O EIEs) provides new insights into the O2 activation through an inner-sphere mechanism at a non-heme iron center.",

author = "Mirica, {Liviu M.} and McCusker, {Kevin P.} and Munos, {Jeffrey W.} and Liu, {Hung Wen} and Klinman, {Judith P.}",

year = "2008",

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T2 - Probing the nature of Fe/O2 intermediates

AU - Mirica, Liviu M.

AU - McCusker, Kevin P.

AU - Munos, Jeffrey W.

AU - Liu, Hung Wen

AU - Klinman, Judith P.

PY - 2008/7/2

Y1 - 2008/7/2

N2 - Contrasted here are the competitive 18O/16O kinetic isotope effects (18O KIEs) on kcat/Km(O2) for three non-heme iron enzymes that activate O2 at an iron center coordinated by a 2-His-1-carboxylate facial triad: taurine dioxygenase (TauD), (S)-(2)-hydroxypropylphosphonic acid epoxidase (HppE), and 1-aminocyclopropyl-1-carboxylic acid oxidase (ACCO). Measured 18O KIEs of 1.0102 ± 0.0002 (TauD), 1.0120 ± 0.0002 (HppE), and 1.0215 ± 0.0005 (ACCO) suggest the formation in the rate-limiting step of O2 activation of an FeIII-peroxohemiketal, FeIII-OOH, and FeIV=O species, respectively. The comparison of the measured 18O KIEs with calculated or experimental 18O equilibrium isotope effects (18O EIEs) provides new insights into the O2 activation through an inner-sphere mechanism at a non-heme iron center.

AB - Contrasted here are the competitive 18O/16O kinetic isotope effects (18O KIEs) on kcat/Km(O2) for three non-heme iron enzymes that activate O2 at an iron center coordinated by a 2-His-1-carboxylate facial triad: taurine dioxygenase (TauD), (S)-(2)-hydroxypropylphosphonic acid epoxidase (HppE), and 1-aminocyclopropyl-1-carboxylic acid oxidase (ACCO). Measured 18O KIEs of 1.0102 ± 0.0002 (TauD), 1.0120 ± 0.0002 (HppE), and 1.0215 ± 0.0005 (ACCO) suggest the formation in the rate-limiting step of O2 activation of an FeIII-peroxohemiketal, FeIII-OOH, and FeIV=O species, respectively. The comparison of the measured 18O KIEs with calculated or experimental 18O equilibrium isotope effects (18O EIEs) provides new insights into the O2 activation through an inner-sphere mechanism at a non-heme iron center.

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