Enterobactin

General description

Enterobactin synthesis occurs via nonribosomal peptide synthetases. The precursor chorismic acid is converted to intermediates isochorismate, 2,3-dihydro-2,3-dihydroxybenzoate and 2,3-dihydroxybenzoic acid (DHB). Final step involves the DHB and L-serine amide linkage. A total of six enzymes (ent A −F) mediate enterobactin biosynthesis.

Application

Enterobactin has been used:

• as a positive control in tryptophan fluorescence quenching experiments
• as a reference standard in high performance liquid chromatography to quantify Kosakonia radicincitans culture medium siderophores
• in the crystallization reservoir to remove iron contamination in the medium and in Fe-enterbactin binding studies

This preparation of enterobactin is not bound to iron and will bind to Fe³⁺ and Fe²⁺ in solution.

Biochem/physiol Actions

Iron mobilization and uptake by microbes is mediated by low molecular weight complexing agents named siderophores. Enterobactin is a catechol (a benzenediol, C₆H₄(OH)₂) type siderophore produced in small quantities by Escherichia coli and related enteric bacteria when grown on iron deficient media, and is one of the most powerful ferric ion complexing agents known. Enterobactin is a very effective sequestering agent for iron, able to remove iron from proteins, insoluble iron complexes, and other siderophores. Studies of the chemistry, regulation, synthesis, recognition, and transport of enterobactin make it the best-understood siderophore.