IUBMB Enzyme Nomenclature


Accepted name: N2-citryl-N6-acetyl-N6-hydroxylysine synthase

Reaction: 2 ATP + citrate + N6-acetyl-N6-hydroxy-L-lysine + H2O = 2 ADP + 2 phosphate + N6-acetyl-N2-citryl-N6-hydroxy-L-lysine

For diagram of reaction click here

Glossary: citryl = 3-hydroxy-3,4-dicarboxybutanoyl

Other name(s): Nα-citryl-Nε-acetyl-Nε-hydroxylysine synthase; iucA (gene name)

Systematic name: citrate:N6-acetyl-N6-hydroxy-L-lysine ligase (AMP-forming)

Comments: Requires Mg2+. The enzyme is involved in the biosynthesis of aerobactin, a dihydroxamate siderophore. It belongs to a class of siderophore synthases known as type A nonribosomal peptide synthase-independent synthases (NIS). Type A enzymes are responsible for the formation of amide or ester bonds between polyamines or amino alcohols and a prochiral carboxyl group of citrate. The enzyme is believed to form an adenylate intermediate prior to ligation.

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


1. Gibson, F. and Magrath, D.I. The isolation and characterization of a hydroxamic acid (aerobactin) formed by Aerobacter aerogenes 62-I. Biochim. Biophys. Acta 192 (1969) 175-184. [PMID: 4313071]

2. Maurer, P.J. and Miller, M. Microbial iron chelators: total synthesis of aerobactin and its constituent amino acid, N6-acetyl-N6-hydroxylysine. J. Am. Chem. Soc. 104 (1982) 3096-3101.

3. de Lorenzo, V., Bindereif, A., Paw, B.H. and Neilands, J.B. Aerobactin biosynthesis and transport genes of plasmid ColV-K30 in Escherichia coli K-12. J. Bacteriol. 165 (1986) 570-578. [PMID: 2935523]

4. Appanna, D.L., Grundy, B.J., Szczepan, E.W. and Viswanatha, T. Aerobactin synthesis in a cell-free system of Aerobacter aerogenes 62-1. Biochim. Biophys. Acta 801 (1984) 437-443.

5. Challis, G.L. A widely distributed bacterial pathway for siderophore biosynthesis independent of nonribosomal peptide synthetases. ChemBioChem 6 (2005) 601-611. [PMID: 15719346]

6. Oves-Costales, D., Kadi, N. and Challis, G.L. The long-overlooked enzymology of a nonribosomal peptide synthetase-independent pathway for virulence-conferring siderophore biosynthesis. Chem. Commun. (Camb.) (2009) 6530-6541. [PMID: 19865642]

[EC created 2012, modified 2019]

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