<P> Calcium ion has a role in regulation of PDC in muscle tissue, because it activates PDP, stimulating glycolysis on its release into the cytosol - during muscle contraction . </P> <P> 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 the transport protein pyruvate translocase . Pyruvate translocase transports pyruvate in a symport fashion with a proton, and hence is active, consuming energy . </P> <P> Upon entry to the mitochondria, the pyruvate is decarboxylated, producing acetyl CoA . 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 . </P> <P> In prokaryotes, which have no mitochondria, this reaction is either carried out in the cytosol, or not at all . </P>

Is the conversion of pyruvate to acetyl coa reversible