Editing Pyruvate dehydrogenase complex (section)

==Localization of pyruvate decarboxylation==
In [[eukaryote|eukaryotic]] cells the [[pyruvate decarboxylation]] occurs inside the mitochondrial matrix, after transport of the substrate, pyruvate, from the [[cytosol]]. The transport of pyruvate into the mitochondria is via the [[transport protein]] pyruvate translocase.  Pyruvate translocase transports pyruvate in a symport fashion with a proton (across the inner mitochondrial membrane), which may be considered to be a form of secondary active transport, but further confirmation/support may be needed for the usage of "secondary active transport" desciptor here (Note: the pyruvate transportation method via the pyruvate translocase appears to be coupled to a proton gradient according to S. Papa et al., 1971, seemingly matching secondary active transport in definition).<ref>{{cite journal |last1=Papa |first1=S |title=The transport of pyruvate in rat liver mitochondria |journal=FEBS Lett. |date= 30 January 1971|volume=12 |issue=5 |pages=285–288 |doi=10.1016/0014-5793(71)80200-4 |pmid=11945601 |doi-access=free }}</ref>

Alternative sources say "transport of pyruvate across the outer mitochondrial membrane appears to be easily accomplished via large non-selective channels such as [[voltage-dependent anion channels]], which enable passive diffusion" and transport across inner mitochondrial membrane is mediated by mitochondrial pyruvate carrier 1 (MPC1) and [[mitochondrial pyruvate carrier 2]] (MPC2).<ref>{{cite journal |last1=Rutter |first1=Jared |title=The long and winding road to the mitochondrial pyruvate carrier |journal=Cancer & Metabolism |date= 23 January 2013|volume=1 |issue=1 |page=6 |doi=10.1186/2049-3002-1-6 |pmid=24280073|pmc=3834494 |doi-access=free }}</ref>

Upon entry into the mitochondrial matrix, the pyruvate is decarboxylated, producing acetyl-CoA (and carbon dioxide and NADH). This irreversible reaction traps the [[acetyl-CoA]] within the mitochondria (the acetyl-CoA can only be transported out of the mitochondrial matrix under conditions of high oxaloacetate via the citrate shuttle, a TCA intermediate that is normally sparse). The carbon dioxide produced by this reaction is [[nonpolar]] and small, and can diffuse out of the mitochondria and out of the cell.{{Citation needed|date=December 2023}}

In [[prokaryote]]s, which have no mitochondria, this reaction is either carried out in the cytosol, or not at all.{{Citation needed|date=December 2023}}