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Related Concept Videos

Fates of Pyruvate01:20

Fates of Pyruvate

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Pyruvate is the end product of glycolysis, where glucose is oxidized to pyruvate, simultaneously reducing NAD+ to NADH. Two molecules of ATP are also produced by substrate-level phosphorylation.
In aerobic organisms, pyruvate is metabolized via the citric acid cycle to produce reduced coenzymes NADH and FADH2. These coenzymes are then oxidized in the electron transport chain to produce ATP and, in the process, regenerate the NAD+ and FAD. As seen in some cell types and organisms, fermentation...
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Fermentation01:29

Fermentation

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Most eukaryotic organisms require oxygen to survive and function adequately. Such organisms produce large amounts of energy during aerobic respiration by metabolizing glucose and oxygen into carbon dioxide and water. However, most eukaryotes can generate some energy in the absence of oxygen by anaerobic metabolism.
Fermentation is a type of metabolic process that occurs in the absence of oxygen, where organic molecules such as glucose are broken down to produce energy. During this process, the...
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Pyruvate Oxidation01:15

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.
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
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Microbial Fermentation01:23

Microbial Fermentation

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Fermentation is a crucial anaerobic metabolic process that enables microbes to derive energy from sugar without relying on oxygen or an electron transport chain. This process is fundamental to various biological and industrial applications and is classified based on the metabolic products generated.Role of Pyruvate in FermentationPyruvate and its derivatives serve as key electron acceptors in fermentative pathways. The oxidation of NADH to regenerate NAD+ is essential for the continuation of...
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Respiration Pathways01:26

Respiration Pathways

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Cellular respiration is a fundamental metabolic process that enables organisms to generate energy from organic molecules. One of its central pathways is the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle, which plays a crucial role in energy production and biosynthetic processes.Conversion of Pyruvate to Acetyl-CoAThe pyruvate generated from glycolysis undergoes oxidative decarboxylation by the pyruvate dehydrogenase complex, producing acetyl-CoA, one molecule of NADH, and one...
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Products of the Citric Acid Cycle00:53

Products of the Citric Acid Cycle

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The cells of most organisms—including plants and animals—obtain usable energy through aerobic respiration, the oxygen-requiring version of cellular respiration. Aerobic respiration consists of four major stages: glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation. The third major stage, the citric acid cycle, is also known as the Krebs cycle or tricarboxylic acid (TCA) cycle.
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Related Experiment Video

Updated: Apr 1, 2026

Liquid Chromatography Coupled to Refractive Index or Mass Spectrometric Detection for Metabolite Profiling in Lysate-based Cell-free Systems
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Fermentative Pyruvate and Acetyl-Coenzyme A Metabolism.

R Gary Sawers, David P Clark

    Ecosal Plus
    |October 8, 2015
    PubMed
    Summary

    Pyruvate formate lyase (PFL) is key in enterobacteria fermentation, converting pyruvate to acetyl-CoA and formate. Its regulation impacts central metabolism, influencing pathways like acetate and ethanol production, and D-lactate formation in mutants.

    Area of Science:

    • Microbiology
    • Biochemistry
    • Metabolic Engineering

    Background:

    • Central metabolism relies on pyruvate and acetyl-CoA.
    • Mixed-acid fermentation in enterobacteria features pyruvate formate lyase (PFL) activity.
    • Formic acid from pyruvate cleavage contributes significantly to carbon flux.

    Purpose of the Study:

    • To elucidate the regulatory mechanisms of pyruvate metabolism in enterobacteria.
    • To understand the role of PFL and its activase in central carbon flow.
    • To differentiate fermentation pathways leading to acetate, ethanol, or 2,3-butanediol.

    Main Methods:

    • Enzyme kinetics studies of pyruvate formate lyase and related enzymes.
    • Analysis of metabolic flux in wild-type and mutant enterobacteria strains.

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  • Investigating the control of PFL activation by PFL-activase.
  • Assessing the impact of NADH:NAD+ ratio on fermentation product formation.

    • Main Results:

    • PFL catalyzes pyruvate to acetyl-CoA and formate, a key step in mixed-acid fermentation.
    • Acetyl-CoA metabolism branches into acetate or ethanol production, regulated by cellular energy demands (ATP) and redox balance (NADH).
    • Mutants lacking acetate or ethanol pathways redirect pyruvate to D-lactate via D-lactate dehydrogenase when PFL is inactive.
    • Some enterobacteria (e.g., Klebsiella) produce 2,3-butanediol via α-acetolactate synthase (ALS) and subsequent reactions, differing from the typical mixed-acid pathway.

    Conclusions:

    • The PFL-catalyzed reaction is central to enterobacterial fermentation, with its activity and downstream acetyl-CoA metabolism tightly regulated.
    • Cellular redox state (NADH:NAD+ ratio) and energy requirements dictate the metabolic fate of pyruvate and acetyl-CoA.
    • Alternative fermentation pathways, such as 2,3-butanediol production, exist in certain enterobacterial genera, highlighting metabolic diversity.