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Pyruvate Oxidation

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After glycolysis, the charged pyruvate molecules enter the mitochondria via active transport and undergo three enzymatic reactions. These reactions ensure that pyruvate can enter the next metabolic pathway so that energy stored in the pyruvate molecules can be harnessed by the cells.
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Related Experiment Video

Updated: Jun 28, 2025

$Liquid Chromatography Coupled to Refractive Index or Mass Spectrometric Detection for Metabolite Profiling in Lysate-based Cell-free Systems$

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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

Keywords:

Electron transport chain Lactate dehydrogenase Lactate metabolism Paracoccus denitrificans Respiration

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Published on: October 3, 2018

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.