Vitamin K2 mediates electron transport from NADH dehydrogenase 2 to bd-type quinol oxidase in Lacticaseibacillus rhamnosus CM MSU 529статьяИсследовательская статья
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Аннотация:Lacticaseibacillus rhamnosus CM MSU 529 was grown in a batch culture under intensive aeration in the presence of 38 mkM hemin and 18 mkM vitamin K2 as a source of menaquinone to activate respiratory metabolism. Unsupplemented aerobic culture served as a control. Supplementation of the growth mediumwith hemin or menaquinone alone had no significant effect on the culture growth. Respiratory conditions (hemin + K2) yielded a biomass of 2.86 ± 0.05 g dw cells/L for a 24-h culture; the molar growth yield YP/S after 18 h of cultivation was 25.6 ± 1.5 g dw cells/mol of glucose consumed. Both values were 27% higher compared to those for the aerobic conditions. Spectral analysis revealed the presence of cytochromes of b- and d-types in membranes of L. rhamnosus CM MSU 529. The activity of the bacterial electron transport chain was investigated using polarography. Membrane preparations of cells grown aerobically on heminsupplemented medium intensively consumed oxygen in the presence of 1 mM NADH. The addition of 0.2 mM menaquinone to the reaction mixture was accompanied by a 4.6-fold increase in NADH oxidation rate. Enzymes presumably involved in NADH oxidation with membranes and identified using MALDI-TOF MS/MS included pyridine nucleotide-disulfide oxidoreductase (Nox-2), NADH dehydrogenase 2 (Ndh-2), and ubiquinol oxidase bd subunit I (CydA). Therefore, in NADH oxidation, 80% of electron transport from NADH to oxygen occurred via Ndh-2, menaquinone, and bd-type quinol oxidase; as little as 20% were transportedvia Nox-2. The study reports experimental evidence to support electron transport chain functioningin L. rhamnosus CM MSU 529 under aerobic cultivation in the presence of hemin and menaquinone. The NADH oxidation rates of membrane preparations of lactic acid bacteria were measured for the first time. Additionally, this is the first time when the property of exogenous menaquinone to transfer electrons from Ndh-2 to bd-type quinol oxidase was demonstrated in vitro in lactic acid bacteria.
