The Enzyme Database

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EC 4.1.99.25     
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
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 4.1.99.24, L-tyrosine isonitrile synthase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
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. [DOI] [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. [DOI] [PMID: 28212039]
[EC 4.1.99.25 created 2018]
 
 


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