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1.	Bhagi-Damodaran, Ambika, et al. (author) Insights Into How Heme Reduction Potentials Modulate Enzymatic Activities of a Myoglobin-based Functional Oxidase 2017 In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 56:23, s. 6622-6626 Journal article (peer-reviewed)abstract Heme-copper oxidase (HCO) is a class of respiratory enzymes that use a heme-copper center to catalyze O-2 reduction to H2O. While heme reduction potential (E degrees') 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 degrees' modulates oxidase activity. Rapid stopped-flow kinetic measurements show that increasing heme E degrees' by ca. 210 mV results in increases in electron transfer (ET) rates by 30-fold, rate of O-2 binding by 12-fold, O-2 dissociation by 35-fold, while decreasing O-2 affinity by 3-fold. Theoretical calculations reveal that E degrees' modulation has significant implications on electronic charge of both heme iron and O-2, resulting in increased O-2 dissociation and reduced O-2 affinity at high E degrees' values. Overall, this work suggests that fine-tuning E degrees' in HCOs and other heme enzymes can modulate their substrate affinity, ET rate and enzymatic activity.

Bhagi-Damodaran, Ambika, et al. (author)
Insights Into How Heme Reduction Potentials Modulate Enzymatic Activities of a Myoglobin-based Functional Oxidase
2017
In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 56:23, s. 6622-6626
Journal article (peer-reviewed)abstract
- Heme-copper oxidase (HCO) is a class of respiratory enzymes that use a heme-copper center to catalyze O-2 reduction to H2O. While heme reduction potential (E degrees') 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 degrees' modulates oxidase activity. Rapid stopped-flow kinetic measurements show that increasing heme E degrees' by ca. 210 mV results in increases in electron transfer (ET) rates by 30-fold, rate of O-2 binding by 12-fold, O-2 dissociation by 35-fold, while decreasing O-2 affinity by 3-fold. Theoretical calculations reveal that E degrees' modulation has significant implications on electronic charge of both heme iron and O-2, resulting in increased O-2 dissociation and reduced O-2 affinity at high E degrees' values. Overall, this work suggests that fine-tuning E degrees' in HCOs and other heme enzymes can modulate their substrate affinity, ET rate and enzymatic activity.

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