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Catabolic Pathways for Alanine, Glycine, Serine, Cysteine, Tryptophan and Threonine

This image is a scaled-down version of the actual pathway image. It does not contain any links to the protein information pages.


Five amino acids, Alanine, Cysteine, Glycine, Serine and Threonine are broken down to yield Pyruvate. Tryptophan is included in this group since one of its breakdown products is Alanine, which is transaminated to Pyruvate. Alanine is important in intertissue nitrogen transport as part of the Glucose-Alanine cycle. Alanine s catabolic pathway involves a simple Aminotransferase reaction that directly produces Pyruvate. Generally Pyruvate produced by this pathway will result in the formation of Oxaloacetate, although when the energy charge of a cell is low the Pyruvate will be oxidized to CO2 and H2O via the PDH complex and the TCA cycle. This makes Alanine a glucogenic amino acid.

Serine is converted to Pyruvate through dehydration by Serine Dehydratase. This PLP-enzyme, like the amino-transferases, functions by forming [...]


1.Genetic manipulation of glycine decarboxylation.
Bauwe H, Kolukisaoglu U.
J Exp Bot. 2003 Jun;54(387):1523-35. Epub 2003 Apr 28.
2.l-Threonine aldolase, serine hydroxymethyltransferase and fungal alanine racemase. A subgroup of strictly related enzymes specialized for different functions.
Contestabile R, Paiardini A, Pascarella S, di Salvo ML, D'Aguanno S, Bossa F.
Eur J Biochem. 2001 Dec;268(24):6508-25.
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