Preparations of Terminal Oxidase Cytochrome bd-II Isolated from Escherichia coli Reveal Significant Hydrogen Peroxide Scavenging Activity

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Elena Forte¹, Martina R. Nastasi¹, and Vitaliy B. Borisov^2,a*

¹Department of Biochemical Sciences, Sapienza University of Rome, I-00185 Rome, Italy

²Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia

^* To whom correspondence should be addressed.

Received April 5, 2022; Revised April 29, 2022; Accepted April 29, 2022

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Cytochrome bd-II is one of the three terminal quinol oxidases of the aerobic respiratory chain of Escherichia coli. Preparations of the detergent-solubilized untagged bd-II oxidase isolated from the bacterium were shown to scavenge hydrogen peroxide (H₂O₂) with high rate producing molecular oxygen (O₂). Addition of H₂O₂ to the same buffer that does not contain enzyme or contains thermally denatured cytochrome bd-II does not lead to any O₂ production. The latter observation rules out involvement of adventitious transition metals bound to the protein. The H₂O₂-induced O₂ production is not susceptible to inhibition by N-ethylmaleimide (the sulfhydryl binding compound), antimycin A (the compound that binds specifically to a quinol binding site), and CO (diatomic gas that binds specifically to the reduced heme d). However, O₂ formation is inhibited by cyanide (IC₅₀ = 4.5 ± 0.5 µM) and azide. Addition of H₂O₂ in the presence of dithiothreitol and ubiquinone-1 does not inactivate cytochrome bd-II and apparently does not affect the O₂ reductase activity of the enzyme. The ability of cytochrome bd-II to detoxify H₂O₂ could play a role in bacterial physiology by conferring resistance to the peroxide-mediated stress.

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KEY WORDS: respiratory chain, terminal oxidase, cytochrome, heme, reactive oxygen species

DOI: 10.1134/S0006297922080041

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