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In [[protein catabolism]], [[protein]]s are broken down by [[protease]]s into their constituent amino acids. Their carbon skeletons (i.e. the de-aminated amino acids) may either enter the citric acid cycle as intermediates (e.g. ''alpha-ketoglutarate'' derived from glutamate or glutamine), having an anaplerotic effect on the cycle, or, in the case of [[leucine]], [[isoleucine]], [[lysine]], [[phenylalanine]], [[tryptophan]], and [[tyrosine]], they are converted into ''acetyl-CoA'' which can be burned to CO<sub>2</sub> and water, or used to form [[ketone bodies]], which too can only be burned in tissues other than the liver where they are formed, or excreted via the urine or breath. These latter amino acids are therefore termed "ketogenic" amino acids, whereas those that enter the citric acid cycle as intermediates can only be cataplerotically removed by entering the gluconeogenic pathway via ''malate'' which is transported out of the mitochondrion to be converted into cytosolic oxaloacetate and ultimately into [[glucose]]. These are the so-called "glucogenic" amino acids. De-aminated alanine, cysteine, glycine, serine, and threonine are converted to pyruvate and can consequently either enter the citric acid cycle as ''oxaloacetate'' (an anaplerotic reaction) or as ''acetyl-CoA'' to be disposed of as CO<sub>2</sub> and water.

Translations:Citric acid cycle/37/en - Revision history

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