TDH tetramer oxidises L-Thr to 2A-3OB

Stable Identifier
Reaction [transition]
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 the first step, L-threonine (L-Thr) is oxidised to 2-amino-3-oxobutanoate (2A-3OBU) using NAD+ as acceptor. This reaction is catalysed by mitochondrial L-threonine 3-dehydrogenase (TDH) (Edgar 2002). The human activity is inferred from the characterised porcine Tdh (Edgar 2002b, Kao & Davis 1994). TDH is thought to exist as a tetramer on the mitochondrial inner membrane in complex with dimeric 2-amino-3-ketobutyrate coenzyme A ligase (GCAT), the second enzyme in this pathway (Tressel et al. 1986). 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.

Literature References
PubMed ID Title Journal Year
12361482 The human L-threonine 3-dehydrogenase gene is an expressed pseudogene

Edgar, AJ

BMC Genet. 2002
7827500 Purification and structural characterization of porcine L-threonine dehydrogenase

Davis, L, Kao, YC

Protein Expr. Purif. 1994
3536927 Interaction between L-threonine dehydrogenase and aminoacetone synthetase and mechanism of aminoacetone production

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

J. Biol. Chem. 1986
12097150 Molecular cloning and tissue distribution of mammalian L-threonine 3-dehydrogenases

Edgar, AJ

BMC Biochem. 2002
Catalyst Activity

L-threonine 3-dehydrogenase activity of PXLP-GCAT dimer:TDH tetramer [mitochondrial inner membrane]

Cross References
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