TDH (L-threonin dehydrogenase)

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Human Uniqueness Compared to "Great Apes": 
Absolute Difference
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L-Threonine Dehydrogenase (TDH) is a human lineage specific expressed pseudogene. In organisms where TDH is functional, it catalyzes the first two steps in one of two L-threonine degredation pathways by conversion of L-threonine to glycine. In humans, 3 mutations in the gene lead to a truncated non-functional protein and as such humans degrade L-threonine via the alternative pathway.


Timing of appearance of the difference in the Hominin Lineage as a defined date or a lineage separation event. The point in time associated with lineage separation events may change in the future as the scientific community agrees upon better time estimates. Lineage separation events are defined in 2017 as:

  • the Last Common Ancestor (LCA) of humans and old world monkeys was 25,000 - 30,000 thousand (25 - 30 million) years ago
  • the Last Common Ancestor (LCA) of humans and chimpanzees was 6,000 - 8,000 thousand (6 - 8 million) years ago
  • the emergence of the genus Homo was 2,000 thousand (2 million) years ago
  • the Last Common Ancestor (LCA) of humans and neanderthals was 500 thousand years ago
  • the common ancestor of modern humans was 100 - 300 thousand years ago

Definite Appearance: 
6,000 thousand years ago
Genetics Topic Attributes
Gene symbols follow the HUGO Gene Nomenclature Committee standard.
Gene Symbol Type of Human-Specific Changes
TDH Pseudogenization


  1. Divergence, demography and gene loss along the human lineage., Kim, Hie Lim, Igawa Takeshi, Kawashima Ayaka, Satta Yoko, and Takahata Naoyuki , Philos Trans R Soc Lond B Biol Sci, 2010 Aug 27, Volume 365, Issue 1552, p.2451-7, (2010)
  2. The human L-threonine 3-dehydrogenase gene is an expressed pseudogene., Edgar, Alasdair J. , BMC Genet, 2002 Oct 2, Volume 3, p.18, (2002)