Journal
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
Volume 56, Issue 23, Pages 6622-6626Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201701916
Keywords
electron transfer; heme proteins; oxidoreductases; oxygen activation; redox chemistry
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Funding
- US National Institute of Health [GM062211]
- Faculty of Science at Stockholm University
- NSF [CHE-1300912]
- Schlumberger foundation Faculty for the Future fellowship
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1300912] Funding Source: National Science Foundation
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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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