Lactate oxidation in Paracoccus denitrificans.
Geumsoo Kim1, Raul Covian2, Lanelle Edwards2
1Laboratory of Biochemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
Archives of Biochemistry and Biophysics
|April 17, 2024
Summary
Paracoccus denitrificans metabolizes lactate using two novel lactate dehydrogenases, D-iLDH and L-iLDH, which do not require NAD+. This provides direct entry for lactate
Area of Science:
- Microbiology
- Biochemistry
- Cellular Respiration
Background:
- Paracoccus denitrificans serves as a model for mammalian mitochondria due to its similar electron transport chain.
- Previous studies focused on respiration with glucose or malate, noting unexplained lactate accumulation.
- The bacterium lacks a typical NAD+-dependent lactate dehydrogenase, prompting investigation into lactate metabolism.
Purpose of the Study:
- To elucidate the mechanisms of lactate oxidation in Paracoccus denitrificans.
- To identify the enzymes responsible for lactate metabolism in this bacterium.
Main Methods:
- Growth studies using d-lactate and l-lactate.
- Proteomic, metabolomic, and biochemical analyses.
- Cloning, production, and characterization of D-lactate preferring enzyme (D-iLDH).
Main Results:
- Paracoccus denitrificans efficiently grows on both d-lactate and l-lactate, supporting high respiratory rates.
- Two non-NAD+-dependent lactate dehydrogenases (D-iLDH and L-iLDH) mediate lactate metabolism.
- Characterized D-iLDH shows high affinity for d-lactate, utilizes quinone as an electron acceptor, and converts lactate to pyruvate.
Conclusions:
- Lactate metabolism in P. denitrificans is primarily mediated by novel, non-NAD+-dependent lactate dehydrogenases.
- D-iLDH provides a direct pathway for lactate-derived reducing equivalents into the electron transport chain.
- This mechanism explains the bacterium's high respiratory capacity when utilizing lactate as a substrate.
Keywords:
Electron transport chainLactate dehydrogenaseLactate metabolismParacoccus denitrificansRespirationMore Related Videos
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