What is the intermediate between pyruvate and the citric acid cycle?

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The reducing power at this stage is largely conserved as NADH and ubiquinol (UQH2) in the mitochondrial inner membrane prior to a series of oxidation reactions that end in water. These oxidations power the translocation of protons from the matrix to the intermembrane space. This leads to a potential gradient (proton pump) that drives the retro-location of protons to the matrix and thus activates ATP synthase, which catalyzes ATP formation.

Where does the Krebs cycle take place?

The TCA cycle was first observed in the muscle tissue of a pigeon. It takes place in all eukaryotic and prokaryotic cells. In eukaryotes, it occurs in the matrix of the mitochondrion. In prokaryotes, it takes place in the cytosol.

Krebs cycle products

Before the Krebs cycle begins, a glucose molecule must be converted to acetyl-CoA. This process yields 2 acetyl-CoA molecules to be fed into the cycle. Thus, the cycle proceeds twice per original glucose, yielding twice the products shown below.

One TCA cycle "turn" yields 7 products:

• GTP
• 3 NADH
• FADH2, which is converted to UQH2 in the presence of coenzyme Q (ubiquinone)
• 2 CO2 (carbon dioxide)

What is pyruvate?

Pyruvate is a biological molecule and product of glucose metabolism that reacts with adenosine triphosphate and carbon dioxide, converting it into acetyl-CoA and adenosine diphosphate (ADP) at the beginning of the TCA cycle. It is often included in the introductory or preliminary step of the cycle.

Pyruvate usually derives from the glycolysis product pyruvic acid, which quickly dissociates in most natural systems, leaving pyruvate.

Pyruvate plays an important role in multiple biotransformations, as explained in greater depth in the article Pyruvate Transformations.

History of the Krebs cycle

German chemist Hans Adolf Krebs' discovery of this cycle in 1937 marked a milestone in biochemistry. Krebs received the Nobel Prize for Physiology or Medicine in 1953 for this contribution to the study of intermediary metabolism in the oxidative breakdown of carbohydrates. Krebs and his coauthor William Arthur Johnson published their findings "The role of citric acid in intermediate metabolism in animal tissues" in Enzymologia after being rejected by Nature. That original publication was followed by many more.

The TCA cycle in research

The TCA cycle is of special interest to researchers in the field of metabolomics. By studying the rates, by-products, enzymatic activity, and other qualities of processes of metabolism, researchers can draw conclusions about diseases and investigate the efficacy of therapies.

Key TCA cycle enzymes

• Malic dehydrogenase
• α-Ketoglutarate dehydrogenase
• Citrate synthase
• Fumarase
• Aconitase

TCA cycle applications

These TCA-related metabolic applications are commonly studied using stable isotope-labeled compounds and mass spectrometry:

• Lipid Metabolism
• Amino Acid Metabolism
• Protein Metabolism (Turnover)
• Glucose Metabolism
• Energy Expenditure
• Metabolomics

We sell TCA metabolites and enzymes for pinpointing metabolic processes as well as stable isotope-tagged compounds that can aid in measuring rates of whole body metabolism or glucose metabolism. Stable isotope-enriched compounds are metabolically similar to natural homologues, making them safe to use as tracers.

See the materials table below to explore products specific to TCA cycle research, including our Kreb’s Cycle kit that includes all 10 components for monitoring this pathway.

What is an intermediate in citric acid cycle?

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What is pyruvate an intermediate in?