Link reaction
The Link reaction, also known as pyruvate decarboxylation forms an important link between the metabolic pathways of glycolysis and the citric acid or Krebs cycle.
In eukaryotes, the reaction takes place only inside the mitochondrial matrix; in prokaryotes similar reactions take place in the cytoplasm and at the plasma membrane.[1]
To summarize:
- Pyruvate is decarboxylated: CO2 is removed.
- It is added to CoA to form Acetyl CoA
Acetyl CoA is then ready for use in the Krebs Cycle.
The Link reaction is important as acetyl-CoA is needed for the Krebs cycle to happen.
Link Reaction Media
Net reaction for pyruvate dehydrogenase
Simplified mechanism for pyruvate dehydrogenase reaction. The TPP coenzyme is shown with abbreviated substituents.
Pyruvate dehydrogenase E1 subunit of E. coli. Colors represent different chains. Structure determined by Arjunan et al. Biochemistry 2002. Created with PyMol.
The active site for pyruvate dehydrogenase (image created from PDB Code 1NI4) holds TPP through metal ligation to a magnesium ion (purple sphere) and through hydrogen bonding to amino acids. While over 20 amino acids can be found in the active site, amino acids Tyr 89, Arg 90, Gly 136, Val 138, Asp 167, Gly 168, Ala 169, Asn, 196, and His 263 actually participate in hydrogen bonding to hold TPP and pyruvate (not shown here) in the active site.
Diagram showing regulation of the enzyme pyruvate dehydrogenase (PD) by PD kinase and PD phosphatase. This includes regulation by the substrates and products of PD and by ATP and ADP and by Mg2+ and Ca2+ ions.
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Related pages
- Respiration
- Cellular respiration (overview)
- Glycolysis
- Krebs cycle (Citric acid cycle)
References
- ↑ Raven et al. 2008. Biology, 8th edition. McGraw Hill. ISBN 978-0-07-110202-5
Other websites
- Notes on Pyruvate decarboxylation Archived 2008-06-18 at the Wayback Machine