Related Experiment Video
Updated: Jun 21, 2026
08:40
An Optimized Protocol to Analyze Glycolysis and Mitochondrial Respiration in Lymphocytes
Published on: November 21, 2016
An alternative to the glyoxylate shunt
1Microbial Ecology, Department of Biology, University of Konstanz, Konstanz, Germany. bernhard.schink@uni-konstanz.de
Molecular Microbiology
|August 18, 2009
Summary
Scientists discovered a new pathway that replenishes citric acid cycle intermediates, crucial for bacterial growth on acetate when the glyoxylate shunt is absent. This finding expands our understanding of microbial metabolism.
Area of Science:
- Microbial metabolism
- Biochemistry
- Molecular Microbiology
Background:
- The citric acid cycle requires anaplerotic reactions to maintain intermediates.
- The glyoxylate shunt is a known anaplerotic pathway for replenishing cycle intermediates.
- Intermediates are withdrawn for biosynthesis of amino acids and haemin precursors.
Purpose of the Study:
- To document an alternative pathway for replenishing four-carbon intermediates.
- To investigate bacterial growth on acetate in the absence of the glyoxylate shunt.
Main Methods:
- The study by Erb et al. documents a newly discovered reaction sequence.
- Analysis of bacterial growth on acetate.
Main Results:
- A linear pathway forms malate and succinyl-CoA from three acetyl-CoA, CO(2), and HCO(3).
- This pathway replenishes four-carbon intermediates independently of the glyoxylate shunt.
- The pathway was identified in phototrophic anoxygenic bacteria and some aerobic bacteria.
Conclusions:
- This newly discovered pathway provides an alternative to the glyoxylate shunt for replenishing citric acid cycle intermediates.
- The pathway is likely widespread across diverse bacterial metabolic groups.
- This finding enhances understanding of bacterial carbon metabolism and anaplerosis.
Related Concept Videos
01:24Other Glycolytic Pathways
The pentose phosphate pathway (PPP) operates in parallel with glycolysis, facilitating the metabolism of both pentoses and glucose. This pathway consists of two distinct phases: the oxidative and non-oxidative phases. While it does not directly generate ATP, the intermediates formed during the process can integrate into glycolysis, contributing to cellular energy metabolism when required.Oxidative Phase: NADPH ProductionThe oxidative phase of the pentose phosphate pathway is primarily...
01:26Respiration Pathways
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...
01:15Pyruvate Oxidation
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+...
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+...
01:20Fates of Pyruvate
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...
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...
02:36The Citric Acid Cycle
The citric acid cycle, also known as the Krebs cycle or TCA cycle, consists of several energy-generating reactions that yield one ATP molecule, three NADH molecules, one FADH2 molecule, and two CO2 molecules.
01:23Glycolysis
Glycolysis, the Embden-Meyerhof pathway, is a central metabolic pathway involved in glucose catabolism. It is highly conserved across most organisms, reflecting its fundamental role in cellular energy production. This process occurs in the cytoplasm and can function both in the presence and absence of oxygen, making it versatile for various organisms and environmental conditions.Stages of GlycolysisGlycolysis is a ten-step pathway that converts glucose into pyruvate, generating a net gain of...