EC - Threonine ammonia-lyase

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IntEnz Enzyme Nomenclature


Accepted name:
threonine ammonia-lyase
Other names:
L-serine dehydratase
L-threonine deaminase
L-threonine dehydratase
L-threonine hydro-lyase (deaminating)
serine deaminase
threonine deaminase
threonine dehydrase
threonine dehydratase
L-threonine ammonia-lyase
Systematic name:
L-threonine ammonia-lyase (2-oxobutanoate-forming)




Most enzymes that catalyse this reaction are pyridoxal-phosphate-dependent, although some enzymes contain an iron-sulfur cluster instead. The reaction catalysed by both types of enzymes involves the initial elimination of water to form an enamine intermediate (hence the enzyme's original classification as EC, threonine dehydratase), followed by tautomerization to an imine form and hydrolysis of the C-N bond [3,5]. The latter reaction, which can occur spontaneously, is also be catalysed by EC, 2-iminobutanoate/2-iminopropanoate deaminase [5]. The enzymes from a number of sources also act on L-serine, cf. EC, L-serine ammonia-lyase.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UM-BBD , UniPathway
Protein domains and families: PROSITE:PDOC00149
Structural data: CSA , EC2PDB
Gene Ontology: GO:0004794
UniProtKB/Swiss-Prot: (59) [show] [UniProt]


  1. Cohn, M.S. and Phillips, A.T.
    Purification and characterization of a B6-independent threonine dehydratase from Pseudomonas putida.
    Biochemistry 13 : 1208-1214 (1974). [PMID: 4814721]
  2. Nishimura, J.S. and Greenberg, D.M.
    Purification and properties of L-threonine dehydrase of sheep liver.
    J. Biol. Chem. 236 : 2684-2691 (1961). [PMID: 14479973]
  3. Phillips, A.T. and Wood, W.A.
    The mechanism of action of 5'-adenylic acid-activated threonine dehydrase.
    J. Biol. Chem. 240 : 4703-4309 (1965). [PMID: 5321308]
  4. Shizuta, Y., Nakazawa, A., Tokushige, M. and Hayaishi, O.
    Studies on the interaction between regulatory enzymes and effectors. 3. Crystallization and characterization of adenosine 5'-monophosphate-dependent threonine deaminase from Escherichia coli.
    J. Biol. Chem. 244 : 1883-1889 (1969). [PMID: 4889010]
  5. Lambrecht, J. A., Flynn, J. M., Downs, D. M.
    Conserved YjgF protein family deaminates reactive enamine/imine intermediates of pyridoxal 5'-phosphate (PLP)-dependent enzyme reactions.
    J. Biol. Chem. 287 : 3454-3461 (2012). [PMID: 22094463]

[EC created 1961 as EC, transferred 2001 to EC, modified 2014]