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

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.

Kahle, MaximilianStockholms universitet,Institutionen för biokemi och biofysik(Swepub:su)mkahl (författare)
Shi, Yelu (författare)
Zhang, Yong (författare)
Ädelroth, PiaStockholms universitet,Institutionen för biokemi och biofysik(Swepub:su)adelr (författare)
Lu, Yi (författare)
Stockholms universitetInstitutionen för biokemi och biofysik (creator_code:org_t)

Ingår i:Angewandte Chemie International Edition: Wiley56:23, s. 6622-66261433-78511521-3773

Av författaren/redakt...: Bhagi-Damodaran, ...; Kahle, Maximilia ...; Shi, Yelu; Zhang, Yong; Ädelroth, Pia; Lu, Yi

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