From ferribactins which accompany pyoverdins in iron deficient cultures of fluorescent pseudomonads a subunit has been obtained formed by condensation of D-tyrosin with L-2,4-diaminobutyric acid to give 2-(1-R-amino-2-p-hydroxyphenylethyl)-1,4,5,6-tetrahydropyrimidine-4-S′-carboxylic acid (1). Evidence is presented that 1 is the precur or of the typical pyoverdin chromophore 7 a.
Pyoverdin type siderophores produced by six fluorescent Pseudomonas strains isolated from different rhizospheres were purified and characterized. The purified ferri-pyoverdins were tested for their ability to promote the growth of other strains grown under iron deficiency conditions. Only the one obtained from Pseudomonas putida BTP1 did not act as a growth promoter.
The structure of the BTP1 siderophore was elucidated by spectroscopic methods and degradation studies. It turned out that it contains a chromophore which differs from the one typical for pyoverdins insofar as it carries the carboxyl group in 3- rather than in 1-position ((3S)-5-amino-1,2-dihydro-8,9-dihydroxy-3 H -pyrimido[1,2 a]quinoline-3-carboxylic acid). The amino group of the chromophore is substituted with the 5-carboxyl group of ʟ-glutamic acid and its carboxyl group with the N -terminus of the peptide ʟ -A sp -ʟ -A la-ʟ -Asp - ᴅ-N5- Ac - N5- OH - Orn - ʟ - Ser - ʟ - ᴄ - N5- OH - Orn . This isopyoverdin fits into the biogenetic scheme which postulates ferribactins as the precursors of pyoverdins
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