page_title: Pyruvate decarboxylase
section_title: Mechanism
hierarchical_section_title: Pyruvate decarboxylase / Mechanism
caption_attribution_description: English: Mechanism of vitamin B1-catalyzed pyruvate decarboxylation
context_page_description: Pyruvate decarboxylase is a homotetrameric enzyme that catalyses the decarboxylation of pyruvic acid to acetaldehyde and carbon dioxide in the cytoplasm of prokaryotes, and in the cytoplasm and mitochondria of eukaryotes. It is also called 2-oxo-acid carboxylase, alpha-ketoacid carboxylase, and pyruvic decarboxylase. In anaerobic conditions, this enzyme is part of the fermentation process that occurs in yeast, especially of the genus Saccharomyces, to produce ethanol by fermentation. It is also present in some species of fish where it permits the fish to perform ethanol fermentation when oxygen is scarce. Pyruvate decarboxylase starts this process by converting pyruvate into acetaldehyde and carbon dioxide. Pyruvate decarboxylase depends on cofactors thiamine pyrophosphate and magnesium. This enzyme should not be mistaken for the unrelated enzyme pyruvate dehydrogenase, an oxidoreductase, that catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA.
context_section_description: The enzyme splits pyruvate into carbon dioxide and a 2-carbon fragment which is attached to its cofactor TPP.  This 2-carbon fragment is attached to the five membered TPP ring in its ylide form. This is an irreversible step in which it creates the acetaldehyde for the second step of alcoholic fermentation (anaerobic fermentation), in which acetaldehyde is reduced by NADH with alcohol dehydrogenase to ethanol.
caption: Mechanism of pyruvate decarboxylation
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