In enzymology, L-threonine 3-dehydrogenase (), or just threonine dehydrogenase, is an enzyme that participates in the process of breaking down threonine in certain non-human organisms like mice. In particular, it catalyzes the chemical reaction
The two substrates of this enzyme are L-threonine and oxidised nicotinamide adenine dinucleotide (NAD+). Its products are (S)-2-amino-3-ketobutyric acid, reduced NADH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is L-threonine:NAD+ oxidoreductase. Other names in common use include L-threonine dehydrogenase, and threonine 3-dehydrogenase.
In humans
In humans, the homolog gene, TDH, is a non-functional pseudogene. The loss of an acceptor splice site consistently leads to a non-functional truncated protein. The primary pathway for threonine degradation in humans instead starts with threonine ammonia-lyase (aka threonine dehydratase) and produces propionyl-CoA instead of glycine.
Structural studies As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes , , and .
References