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Insights Into How Heme Reduction Potentials Modulate Enzymatic Activities of a Myoglobin-based Functional Oxidase.


ABSTRACT: Heme-copper oxidase (HCO) is a class of respiratory enzymes that use a heme-copper center to catalyze O2 reduction to H2 O. While heme reduction potential (E°') of different HCO types has been found to vary >500?mV, its impact on HCO activity remains poorly understood. Here, we use a set of myoglobin-based functional HCO models to investigate the mechanism by which heme E°' modulates oxidase activity. Rapid stopped-flow kinetic measurements show that increasing heme E°' by ca. 210?mV results in increases in electron transfer (ET) rates by 30-fold, rate of O2 binding by 12-fold, O2 dissociation by 35-fold, while decreasing O2 affinity by 3-fold. Theoretical calculations reveal that E°' modulation has significant implications on electronic charge of both heme iron and O2 , resulting in increased O2 dissociation and reduced O2 affinity at high E°' values. Overall, this work suggests that fine-tuning E°' in HCOs and other heme enzymes can modulate their substrate affinity, ET rate and enzymatic activity.

SUBMITTER: Bhagi-Damodaran A 

PROVIDER: S-EPMC5553066 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Insights Into How Heme Reduction Potentials Modulate Enzymatic Activities of a Myoglobin-based Functional Oxidase.

Bhagi-Damodaran Ambika A   Kahle Maximilian M   Shi Yelu Y   Zhang Yong Y   Ädelroth Pia P   Lu Yi Y  

Angewandte Chemie (International ed. in English) 20170504 23


Heme-copper oxidase (HCO) is a class of respiratory enzymes that use a heme-copper center to catalyze O<sub>2</sub> reduction to H<sub>2</sub> O. While heme reduction potential (E°') of different HCO types has been found to vary >500 mV, its impact on HCO activity remains poorly understood. Here, we use a set of myoglobin-based functional HCO models to investigate the mechanism by which heme E°' modulates oxidase activity. Rapid stopped-flow kinetic measurements show that increasing heme E°' by  ...[more]

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