pyruvate decarboxylation
{{Short description|Conversion of pyruvate into acetyl-CoA}}
File:Pyruvate dehydrogenase complex reaction.svg complex reaction]]
Pyruvate decarboxylation or pyruvate oxidation, also known as the link reaction (or oxidative decarboxylation of pyruvate{{Cite web|date=2018-07-29|title=Oxidative decarboxylation of Pyruvate|url=https://www.biosciencenotes.com/oxidative-decarboxylation-of-pyruvate/|access-date=2021-07-09|website=Bioscience Notes|language=en-US}}), is the conversion of pyruvate into acetyl-CoA by the enzyme complex pyruvate dehydrogenase complex.{{cite web|url=https://www.khanacademy.org/science/biology/cellular-respiration-and-fermentation/pyruvate-oxidation-and-the-citric-acid-cycle/a/pyruvate-oxidation|title=Pyruvate oxidation|website=Khanacademy.org|accessdate=25 January 2018}}{{cite web|url=http://oregonstate.edu/instruct/bb451/winter08/lectures/citricacidcycle.html|title=Pyruvate Oxidation|website=Oregonstate.edu|accessdate=25 January 2018}}
The reaction may be simplified as:
:Pyruvate + NAD+ + CoA → Acetyl-CoA + NADH + CO2
Pyruvate oxidation is the step that connects glycolysis and the Krebs cycle.{{Citation|last=Trifiletti|first=R. R.|title=Thiamine (Vitamin B1) and Beri-Beri|date=2014-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780123851574001160|encyclopedia=Encyclopedia of the Neurological Sciences (Second Edition)|pages=445–447|editor-last=Aminoff|editor-first=Michael J.|place=Oxford|publisher=Academic Press|language=en|doi=10.1016/b978-0-12-385157-4.00116-0|isbn=978-0-12-385158-1|access-date=2020-11-16|editor2-last=Daroff|editor2-first=Robert B.|url-access=subscription}} In glycolysis, a single glucose molecule (6 carbons) is split into 2 pyruvates (3 carbons each). Because of this, the link reaction occurs twice for each glucose molecule to produce a total of 2 acetyl-CoA molecules, which can then enter the Krebs cycle.
Energy-generating ions and molecules, such as amino acids and carbohydrates, enter the Krebs cycle as acetyl coenzyme A and oxidize in the cycle.{{Cite journal|last1=Stryer|first1=Lubert|last2=Tymoczko|first2=John L.|last3=Berg|first3=Jeremy M.|date=2002|title=The Citric Acid Cycle|url=https://www.ncbi.nlm.nih.gov/books/NBK21163/|journal=Biochemistry. 5th Edition|language=en}} The pyruvate dehydrogenase complex (PDC) catalyzes the decarboxylation of pyruvate, resulting in the synthesis of acetyl-CoA, CO2, and NADH. In eukaryotes, this enzyme complex regulates pyruvate metabolism, and ensures homeostasis of glucose during absorptive and post-absorptive state metabolism.{{Cite journal|last1=Jordan|first1=Frank|last2=Furey|first2=William|last3=Nemeria|first3=Natalia S.|last4=Patel|first4=Mulchand S.|date=2014-06-13|title=The Pyruvate Dehydrogenase Complexes: Structure-based Function and Regulation|url=http://www.jbc.org/content/289/24/16615|journal=Journal of Biological Chemistry|language=en|volume=289|issue=24|pages=16615–16623|doi=10.1074/jbc.R114.563148|issn=1083-351X|pmid=24798336|pmc=4059105|doi-access=free}} As the Krebs cycle occurs in the mitochondrial matrix, the pyruvate generated during glycolysis in the cytosol is transported across the inner mitochondrial membrane by a pyruvate carrier under aerobic conditions.{{Citation needed|date=December 2023}}