TY - JOUR
T1 - Spectroscopic Investigations of Catalase Compound II
T2 - Characterization of an Iron(IV) Hydroxide Intermediate in a Non-thiolate-Ligated Heme Enzyme
AU - Yosca, Timothy H.
AU - Langston, Matthew C.
AU - Krest, Courtney M.
AU - Onderko, Elizabeth L.
AU - Grove, Tyler L.
AU - Livada, Jovan
AU - Green, Michael T.
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/12/14
Y1 - 2016/12/14
N2 - We report on the protonation state of Helicobacter pylori catalase compound II. UV/visible, Mössbauer, and X-ray absorption spectroscopies have been used to examine the intermediate from pH 5 to 14. We have determined that HPC-II exists in an iron(IV) hydroxide state up to pH 11. Above this pH, the iron(IV) hydroxide complex transitions to a new species (pKa = 13.1) with Mössbauer parameters that are indicative of an iron(IV)-oxo intermediate. Recently, we discussed a role for an elevated compound II pKa in diminishing the compound I reduction potential. This has the effect of shifting the thermodynamic landscape toward the two-electron chemistry that is critical for catalase function. In catalase, a diminished potential would increase the selectivity for peroxide disproportionation over off-pathway one-electron chemistry, reducing the buildup of the inactive compound II state and reducing the need for energetically expensive electron donor molecules.
AB - We report on the protonation state of Helicobacter pylori catalase compound II. UV/visible, Mössbauer, and X-ray absorption spectroscopies have been used to examine the intermediate from pH 5 to 14. We have determined that HPC-II exists in an iron(IV) hydroxide state up to pH 11. Above this pH, the iron(IV) hydroxide complex transitions to a new species (pKa = 13.1) with Mössbauer parameters that are indicative of an iron(IV)-oxo intermediate. Recently, we discussed a role for an elevated compound II pKa in diminishing the compound I reduction potential. This has the effect of shifting the thermodynamic landscape toward the two-electron chemistry that is critical for catalase function. In catalase, a diminished potential would increase the selectivity for peroxide disproportionation over off-pathway one-electron chemistry, reducing the buildup of the inactive compound II state and reducing the need for energetically expensive electron donor molecules.
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U2 - 10.1021/jacs.6b09693
DO - 10.1021/jacs.6b09693
M3 - Article
C2 - 27960340
AN - SCOPUS:85006314659
SN - 0002-7863
VL - 138
SP - 16016
EP - 16023
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 49
ER -