Threonine is degraded into glycine and the acetyl group in a pathway common to prokaryotic and eukaryotic cells. The pathway is two steps long; the first step is the oxidation of the hydroxy group of threonine to create 2-amino-3-ketobutyrate by L-threonine dehydrogenase. The second step is catalysed by 2-amino-3-ketobutyrate CoA ligase (KBL); this is a PLP-dependent acetyltransferase, transferring the newly formed acetyl group of the substrate to Coenzyme A to give glycine and acetyl-CoA. The two enzymes needed for the pathway form a complex; this is because the aminoketobutyrate intermediate (substrate for KBL) spontaneously decarboxylates in aqueous solution.
Defined by 3 residues: SER:A-188 [auth A-185]HIS:A-216 [auth A-213]LYS:A-247 [auth A-244]