Ferribactins - the Biogenetic Precursors of Pyoverdins [1]

The so-called fluorescent group of Pseudomonas produces peptidic siderophores when grown in an iron deficient medium. They all contain (1S)5-amino-2,3-dihydro-8,9-dihydroxy-1 H-pyrimido[l,2a]-quinoline-l-carboxylic acid (7a) or its 5,6dihydro derivative as a chromophore. The 5-amino group is bound amidically to a small dicarboxylic acid (a member of the citric acid cycle) while the carboxylic group is linked to a peptide residue (not necessarily via its N-terminus). Noth­ ing is known so far about the biogenesis of the chromophore. In 1967 Maurer et al. [2] isolated a peptidic iron complexing pigment from cultures of Pseudomonas fluorescens ATCC 13525 which they named ferribactin and which lacked the typical pyoverdin chromophore. The amino acid compo­ sition determined by Maurer [2] was corrected in 1981 by Philson and Llinas [3, 4] to be