IUBMB Enzyme Nomenclature


Accepted name: L-tryptophan isonitrile synthase

Reaction: L-tryptophan + D-ribulose 5-phosphate = (2S)-3-(1H-indol-3-yl)-2-isocyanopropanoate + hydroxyacetone + formaldehyde + phosphate + H2O

For diagram of reaction click here (mechanism)

Glossary: (2S)-3-(1H-indol-3-yl)-2-isocyanopropanoate = L-tryptophan isonitrile
hydroxyacetone = 1-hydroxypropan-2-one

Other name(s): isnA (gene name); ambI1 (gene name); well1 (gene name)

Systematic name: L-tryptophan:D-ribulose-5-phosphate lyase (isonitrile-forming)

Comments: The enzymes from cyanobacteria that belong to the Nostocales order participate in the biosynthesis of hapalindole-type alkaloids. According to the proposed mechanism, the enzyme forms an imine intermediate composed of linked L-tryptophan and D-ribulose 5-phosphate, followed by loss of the phosphate group and formation of a β-keto imine and keto-enol tautomerization. This is followed by a C-C bond cleavage, the release of hydroxyacetone, and a retro aldol type reaction that releases formaldehyde and forms the final product [3]. cf. EC, L-tyrosine isonitrile synthase

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Brady, S.F. and Clardy, J. Cloning and heterologous expression of isocyanide biosynthetic genes from environmental DNA. Angew Chem Int Ed Engl 44 (2005) 7063-7065. [PMID: 16206308]

2. Brady, S.F. and Clardy, J. Systematic investigation of the Escherichia coli metabolome for the biosynthetic origin of an isocyanide carbon atom. Angew Chem Int Ed Engl 44 (2005) 7045-7048. [PMID: 16217820]

3. Hillwig, M.L., Zhu, Q. and Liu, X. Biosynthesis of ambiguine indole alkaloids in cyanobacterium Fischerella ambigua. ACS Chem. Biol. 9 (2014) 372-377. [PMID: 24180436]

4. Chang, W.C., Sanyal, D., Huang, J.L., Ittiamornkul, K., Zhu, Q. and Liu, X. In vitro stepwise reconstitution of amino acid derived vinyl isocyanide biosynthesis: detection of an elusive intermediate. Org. Lett. 19 (2017) 1208-1211. [PMID: 28212039]

[EC created 2018]

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