Carboxylase

Carboxylase, an enzyme that removes the carboxyl group from organic alpha-keto acids and some beta-keto acids in the form of CO2. Carboxylase was first discovered by Dakin in animal tissues and by Neuberg in yeast. It causes the decarboxylation of pyruvic acid formed during fermentation into acetaldehyde: CH3COCOOH = CH3CHO + CO2 pyruvic acid acetaldehyde

This reaction serves as the source of all fermentation carbon dioxide. Similarly, carboxylase acts on other alpha-keto acids, such as alpha-ketovaleric acid, alpha-ketoglutaric acid, and other acids formed in the body from amino acids during the oxidative removal of their amino groups. Carboxylase is widely distributed in nature: it has been found in the cells of lower and higher plants and in many animal tissues, particularly in the liver and muscles. All carbon dioxide of metabolism (respiration, fermentation) is the product of the combined action of oxidoreductases and carboxylase without the direct participation of atmospheric oxygen. In the body, CO2 is apparently never formed by the direct oxidation of carbon. Its source is always the removal of carboxyl groups by the action of carboxylase on alpha-keto acids formed in intermediate metabolism from the breakdown products of proteins, fats, and carbohydrates under the influence of cellular oxidoreductase enzymes.