Saturday, February 6, 2010

Pyruvate Decarboxylation

Pyruvate decarboxylation, also called oxidative decarboxylation, is the biochemical reaction that uses pyruvate to form acetyl-CoA, releasing NADH, a reducing equivalent, and carbon dioxide via decarboxylation. It is also known as the link reaction because it forms an important link between the metabolic pathways of glycolysis and the citric acid cycle. This reaction is usually catalyzed by the pyruvate dehydrogenase complex as part of aerobic respiration. In eukaryotes, pyruvate decarboxylation takes place exclusively inside the mitochondrial matrix; in prokaryotes similar reactions take place in the cytoplasm and at the plasma membrane.

Pyruvate decarboxylation occurs in the mitochondria, unlike the reactions of glycolysis which are cytosolic, and is very common in most organisms as a link to the citric acid cycle. The conversion of pyruvate to acetyl CoA by the pyruvate dehydrogenase complex is a key step in the liver in particular, as it removes any chance of conversion of pyruvate to glucose, or as a transmination substrate. It commits pyruvate to entering the citric acid cycle, where it is either used as a substrate for oxidative phosphorylation, or is converted to citrate for export to the cytosol to serve as a substrate for fatty acid and isoprenoid biosynthesis.