Cytochrome bd as Antioxidant Redox Enzyme

Abstract

One of the main functions of enzyme complexes that constitute electron transport (respiratory) chains of organisms is to maintain cellular redox homeostasis by oxidizing reducing equivalents, NADH and quinol. Cytochrome bd is a unique terminal oxidase of the chains of many bacteria including pathogenic species. This redox enzyme couples the oxidation of ubiquinol or menaquinol by molecular oxygen to the generation of proton motive force, a universal energy currency. The latter is used by the organism to produce ATP, another cellular energy currency, via oxidative phosphorylation. Escherichia coli contains two bd-type oxidases, bd-I and bd-II, encoded by the cydAB and appCB operons, respectively. Surprisingly, both bd enzymes make a further contribution to molecular mechanisms of maintaining the appropriate redox balance in the bacterial cell by means of elimination of reactive oxygen species, such as hydrogen peroxide. This review summarizes recent data on the redox-modulated H2O2-scavenging activities of cytochromes bd-I and bd-II from E. coli. The possibility of such antioxidant properties in cytochromes bd from other bacteria is also discussed.

Probiotic Characteristics and Anti-Inflammatory Effects of Limosilactobacillus fermentum 664 Isolated from Chinese Fermented Pickles

“…By comparison with the genes and genomes annotated in KEGG, we found that L. fermentum 664 had functional genes associated with antioxidant and anti-inflammatory proteins including Cytochrome bd ubiquinol oxidase subunit I (CydA), Cytochrome bd ubiquinol oxidase subunit II (CydB), and NAD(P)H dehydrogenase quinone 1 (NQO1). Additionally, CydA and CydB can indirectly regulate cellular redox homeostasis by encoding cytochrome bd-type oxidases [ 65 ]. Some studies have shown that NQO1, acting as an endogenous antioxidant, has a mitigating effect on inflammation [ 66 ].…”

Cyanide Insensitive Oxidase Confers Hydrogen Sulfide and Nitric Oxide Tolerance to Pseudomonas aeruginosa Aerobic Respiration

“…A large body of evidence has demonstrated that bd -type oxidases, in addition to sustaining cell bioenergetics, can support virulence in several pathogens by providing protection against several stressors [ 25 ], including antibiotics [ 25 , 34 , 35 ], peroxynitrite [ 36 , 37 ], NO [ 38 , 39 ], hydrogen peroxide (H 2 O 2 ) [ 40 , 41 , 42 ], reactive oxygen species produced by macrophages, and H 2 S [ 43 ]. Significant sulfate concentrations and high H 2 S production have recently been reported in CF individuals infected by P. aeruginosa both at the site of infection and in the expectorate [ 44 , 45 ].…”