Enterobactin

Enterobactin (also known as Enterochelin) is a high affinity siderophore that acquires iron for microbial systems. It is primarily found in Gram-negative bacteria, such as Escherichia coli and Salmonella typhimurium.

Enterobactin is the strongest siderophore known, binding to the ferric ion (Fe) with the affinity (K = 10 M). This value is substantially larger than even some synthetic metal chelators, such as EDTA (K_f,Fe3+ ~ 10 M). Due to its high affinity, enterobactin is capable of chelating even in environments where the concentration of ferric ion is held very low, such as within living organisms. Enterobactin can extract iron even from the air. Pathogenic bacteria can steal iron from other living organisms using this mechanism, even though the concentration of iron is kept extremely low due to the toxicity of free iron.