Expressed in all tissues examined. Detected in most cell types examined, but not observed in endothelial cells, glioma cell lines and some leukemia cell lines. Belongs to the NAD(P)-dependent epimerase/dehydratase family. According to PubMed:12361482, the human TDH gene is an expressed pseudogene encoding non-functional truncated proteins that are unable to make appropriate contacts with the substrates, L-threonine and NAD(+). Although all exons expected to encode a functional L-threonine 3-dehydrogenase of 369 residues are present in the human genome, all transcripts described encode truncated proteins that result from mutations within the gene causing the loss of acceptor splice site preceding exon 4 and exon 6.