Pyridoxal phosphate (PLP) dependent enzyme, which catalyzes the cleavage of 2-amino-3-oxobutanoate to glycine and acetyl-CoA. acetyl-CoA + glycine = (2S)-2-amino-3-oxobutanoate + CoA Translocates to the nucleus upon cold and osmotic stress. Strongly expressed in heart, brain, liver and pancreas. Also found in lung. Belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family. One of the major routes for the degradation of L-threonine to glycine in both prokaryotes and eukaryotes takes place through a two-step biochemical pathway in mitochondria. In the first step, L-threonine is oxidized to (2S)-2-amino-3-oxobutanoate, by L-threonine 3-dehydrogenase tetramer (TDH). In the second step, mitochondrial 2-amino-3-ketobutyrate coenzyme A ligase (GCAT) catalyzes the reaction between (2S)-2-amino-3-oxobutanoate and coenzyme A to form glycine and acetyl-CoA. In human, however the enzyme thats catalyzes the fist reaction, TDH, is an expressed pseudogene encoding non-functional truncated proteins.