IUBMB Enzyme Nomenclature


Accepted name: tryptophanase

Reaction: L-tryptophan + H2O = indole + pyruvate + NH3 (overall reaction)
(1a) L-tryptophan = indole + 2-aminoprop-2-enoate
(1b) 2-aminoprop-2-enoate = 2-iminopropanoate (spontaneous)
(1c) 2-iminopropanoate + H2O = pyruvate + NH3 (spontaneous)

Other name(s): L-tryptophanase; L-tryptophan indole-lyase (deaminating); TNase

Systematic name: L-tryptophan indole-lyase (deaminating; pyruvate-forming)

Comments: A pyridoxal-phosphate protein, requiring K+. The enzyme cleaves a carbon-carbon bond, releasing indole and an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination to form pyruvate and ammonia. The latter reaction, which can occur spontaneously, can also be catalysed by EC, 2-iminobutanoate/2-iminopropanoate deaminase. Also catalyses 2,3-elimination and β-replacement reactions of some indole-substituted tryptophan analogues of L-cysteine, L-serine and other 3-substituted amino acids.

Links to other databases: BRENDA, EXPASY, GTD, KEGG, Metacyc, PDB, CAS registry number: 9024-00-4


1. Burns, R.O. and DeMoss, R.D. Properties of tryptophanase from Escherichia coli. Biochim. Biophys. Acta 65 (1962) 233-244. [PMID: 14017164]

2. Newton, W.A., Morino, Y. and Snell, E.E. Properties of crystalline tryptophanase. J. Biol. Chem. 240 (1965) 1211-1218. [PMID: 14284727]

3. Cowell, J.L., Maser, K. and DeMoss, R.D. Tryptophanase from Aeromonas liquifaciens. Purification, molecular weight and some chemical, catalytic and immunological properties. Biochim. Biophys. Acta 315 (1973) 449-463.

4. Snell, E.E. Tryptophanase: structure, catalytic activities, and mechanism of action. Adv. Enzymol. Relat. Areas Mol. Biol. 42 (1975) 287-333. [PMID: 236639]

[EC created 1972]

Return to EC 4.1.99 home page
Return to EC 4.3 home page
Return to EC 4 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page