Nitric Oxide Does Not Inhibit but Is Metabolized by the Cytochrome bcc-aa3 Supercomplex.
Int J Mol Sci
; 21(22)2020 Nov 12.
Article
em En
| MEDLINE
| ID: mdl-33198276
ABSTRACT
Nitric oxide (NO) is a well-known active site ligand and inhibitor of respiratory terminal oxidases. Here, we investigated the interaction of NO with a purified chimeric bcc-aa3 supercomplex composed of Mycobacterium tuberculosis cytochrome bcc and Mycobacterium smegmatisaa3-type terminal oxidase. Strikingly, we found that the enzyme in turnover with O2 and reductants is resistant to inhibition by the ligand, being able to metabolize NO at 25 °C with an apparent turnover number as high as ≈303 mol NO (mol enzyme)-1 min-1 at 30 µM NO. The rate of NO consumption proved to be proportional to that of O2 consumption, with 2.65 ± 0.19 molecules of NO being consumed per O2 molecule by the mycobacterial bcc-aa3. The enzyme was found to metabolize the ligand even under anaerobic reducing conditions with a turnover number of 2.8 ± 0.5 mol NO (mol enzyme)-1 min-1 at 25 °C and 8.4 µM NO. These results suggest a protective role of mycobacterial bcc-aa3 supercomplexes against NO stress.
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MEDLINE
Assunto principal:
Complexo IV da Cadeia de Transporte de Elétrons
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Complexo III da Cadeia de Transporte de Elétrons
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Idioma:
En
Ano de publicação:
2020
Tipo de documento:
Article