Threonine catabolism

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R-HSA-8849175
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Pathway
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Homo sapiens
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The degradation of L-threonine to glycine in both prokaryotes and eukaryotes takes place through a two-step biochemical pathway in mitochondria (Dale 1978). In the first step, L-threonine is oxidised to 2-amino-3-oxobutanoate. This reaction is catalysed by mitochondrial L-threonine 3-dehydrogenase tetramer (TDH tetramer). In the second step, mitochondrial 2-amino-3-ketobutyrate coenzyme A ligase (GCAT, aka KBL) catalyses the reaction between 2-amino-3-oxobutanoate and coenzyme A to form glycine and acetyl-CoA. GCAT resides on the mitochondrial inner membrane in dimeric form and requires pyridoxal 5-phosphate (PXLP) as cofactor. GCAT is thought to exist on the mitochondrial inner membrane in complex with TDH. With these two enzymes located together, it stops the rapid and spontaneous decarboxylation of 2A-3OBU to aminoacetone and carbon dioxide and instead, results in glycine formation (Tressel et al. 1986).

Literature References
PubMed ID Title Journal Year
3536927 Interaction between L-threonine dehydrogenase and aminoacetone synthetase and mechanism of aminoacetone production

Tressel, T, Thompson, R, Zieske, LR, Menendez, MI, Davis, L

J. Biol. Chem. 1986
728468 Catabolism of threonine in mammals by coupling of L-threonine 3-dehydrogenase with 2-amino-3-oxobutyrate-CoA ligase

Dale, RA

Biochim. Biophys. Acta 1978
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