6CH5

Dehaloperoxidase B in complex with substrate 4-Nitroguaiacol

Summary for 6CH5

• Entry DOI: 10.2210/pdb6ch5/pdb
• Descriptor: Dehaloperoxidase B, PROTOPORPHYRIN IX CONTAINING FE, SULFATE ION, ... (7 entities in total)
• Functional Keywords: oxidoreductase
• Biological source: Amphitrite ornata
• Total number of polymer chains: 2
• Total formula weight: 33093.75

Authors

de Serrano, V.S.,Carey, L.M.,Ghiladi, R.A. (deposition date: 2018-02-21, release date: 2019-01-16, Last modification date: 2023-10-04)

Primary citation

McGuire, A.H.,Carey, L.M.,de Serrano, V.,Dali, S.,Ghiladi, R.A.
Peroxidase versus Peroxygenase Activity: Substrate Substituent Effects as Modulators of Enzyme Function in the Multifunctional Catalytic Globin Dehaloperoxidase.
Biochemistry, 57:4455-4468, 2018

PubMed Abstract: 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 HO-dependent oxidative dehalogenation of 4-haloguaiacols (F, Cl, and Br) to 2-methoxybenzoquinone (2-MeOBQ). O 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 O 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.

PubMed: 29949340
DOI: 10.1021/acs.biochem.8b00540

Experimental method

X-RAY DIFFRACTION (1.65 Å)