Peroxidase versus Peroxygenase Activity: Substrate
Substituent Effects as Modulators of Enzyme Function in the Multifunctional
Catalytic Globin Dehaloperoxidase
Version 2 2018-07-13, 20:14
Version 1 2018-07-13, 17:18
Posted on 2018-07-13 - 20:14
The
dehaloperoxidase-hemoglobin (DHP) from the terebellid polychaete Amphitrite ornata is a multifunctional hemoprotein that
catalyzes the oxidation of a wide variety of substrates, including
halo/nitrophenols, haloindoles, and pyrroles, via peroxidase and/or
peroxygenase mechanisms. To probe whether substrate substituent effects
can modulate enzyme activity in DHP, we investigated its reactiviy
against a panel of o-guaiacol substrates given their
presence (from native/halogenated and non-native/anthropogenic sources)
in the benthic environment that A. ornata inhabits.
Using biochemical assays supported by spectroscopic, spectrometric,
and structural studies, DHP was found to catalyze the H2O2-dependent oxidative dehalogenation of 4-haloguaiacols
(F, Cl, and Br) to 2-methoxybenzoquinone (2-MeOBQ). 18O
labeling studies confirmed that O atom incorporation was derived exclusively
from water, consistent with substrate oxidation via a peroxidase-based
mechanism. The 2-MeOBQ product further reduced DHP to its oxyferrous
state, providing a link between the substrate oxidation and O2 carrier functions of DHP. Nonnative substrates resulted in
polymerization of the initial substrate with varying degrees of oxidation,
with 2-MeOBQ identified as a minor product. When viewed alongside
the reactivity of previously studied phenolic substrates, the results
presented here show that simple substituent effects can serve as functional
switches between peroxidase and peroxygenase activities in this multifunctional
catalytic globin. More broadly, when recent findings on DHP activity
with nitrophenols and azoles are included, the results presented here
further demonstrate the breadth of heterocyclic compounds of anthropogenic
origin that can potentially disrupt marine hemoglobins or function
as environmental stressors, findings that may be important when assessing
the environmental impact of these pollutants (and their metabolites)
on aquatic systems.
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McGuire, Ashlyn
H.; Carey, Leiah M.; Serrano, Vesna de; Dali, Safaa; Ghiladi, Reza A. (2018). Peroxidase versus Peroxygenase Activity: Substrate
Substituent Effects as Modulators of Enzyme Function in the Multifunctional
Catalytic Globin Dehaloperoxidase. ACS Publications. Collection. https://doi.org/10.1021/acs.biochem.8b00540
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AUTHORS (5)
AM
Ashlyn
H. McGuire
LC
Leiah M. Carey
VS
Vesna de Serrano
SD
Safaa Dali
RG
Reza A. Ghiladi