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The reaction is part of the aerobic respiration pathway. Although it is not part of either glycolysis or the citric acid cycle, it is often portrayed as part of one or the other for simplicity.
Additional recommended knowledge
Pyruvate decarboxylation reaction
Coenzyme A is later released from acetyl CoA, during the citric acid cycle. This recycling of the coenzyme allows pyruvate decarboxylation to recur indefinitely under aerobic respiration.
Regulation of pyruvate decarboxylation
Pyruvate dehydrogenase complex catalyzes this reaction and is regulated by several inhibitors and promoters:
These factors have the overall effect of slowing this reaction when there is either little oxygen, or when the cell has a lot of energy (as characterized by the ratios ATP/ADP, NADH/NAD+ and acetyl-CoA/CoASH).
Localization of pyruvate decarboxylation
In eukaryotic cells the pyruvate decarboxylation occurs inside the mitochondria, after transport of the substrate, pyruvate, from the cytosol. The transport of pyruvate into the mitochondria is via a transport protein and is active, consuming energy. Passive diffusion of pyruvate into the mitochondria is impossible because it is a polar molecule.
On entry to the mitochondria the pyruvate decarboxylation occurs, producing acetyl CoA. This irreversible reaction traps the acetyl CoA within the mitochondria (there is no transporter for acetyl CoA). The carbon dioxide produced by this reaction is nonpolar and small, and can diffuse out of the mitochondria and out of the cell.
In prokaryotes, which have no mitochondria, this reaction is either carried out in the cytosol, or not at all.
Post-pyruvate decarboxylation processes
The acetyl CoA produced by this reaction may go on to a variety of different metabolic pathways. The major usage is the citric acid cycle and aerobic respiration, but acetyl CoA is also a major substrate for lipid and amino acid synthesis. Indirectly, intermediates in the citric acid pathway may also be used for synthesis.
The NADH produced may also be used in several ways. Under aerobic conditions, NADH may be oxidized by the electron transport chain into NAD+, renewing this reactant for use in oxidative decarboxylation (this requires oxygen). In anaerobic conditions, NAD+ can be regenerated by anaerobic respiration; however, acetyl coA will quickly build up as it is no longer consumed by the stalled citric acid cycle, and this inhibits the forward reaction.
Pyruvate oxidation is the step which connects glycolysis to Krebs Cycle. It takes the two pyruvate molecules formed during glycolysis and transports them from the cytoplasm, through the two mitochondrial membranes into the mitochondrial matrix. Once inside, a multienzyme complex known as the pyruvate dehydrogenase complex catalyzes these changes:
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pyruvate_decarboxylation". A list of authors is available in Wikipedia.|