Ferrichrome biosynthesis

The majority of Fur-regulated gene products are involved in iron uptake. Genes for transport and biosynthesis of enterobactin have been studied in E. coli K-12 (Earhart, 1996). It is assumed that this system is found in nearly every E. coli strain. Also the ferrichrome transport system seems to have a very broad distribution. The ferric citrate transport system (fee), however, is only present in some E. coli strains and may be part of a pathogenicity island. The aerobactin and yersiniabactin biosynthesis and transport systems are not found in all E. coli strains and are integrated into pathogenicity islands (Schubert et al., 1999). The ability to utilize haem seems also to be a specific pathogenicity-related adaptation. Haem transport systems are used in the animal or human host, where transferrin and lactoferrin create an iron-poor environment for bacteria. 

Growth of Fusariutn sp. at low iron concentration causes the accumulation of a variety of hydroxamic acids of which one has been characterized and named fusarinine, or NS-( s-5-hydroxy-3-methylpent-2-enoyl)-NS-hydroxy-L-ornithine (38). The cis configuration in the unsaturated acyl substituent accounts for the extreme acid lability of the hydroxamic acid bond. Fusarinine is the amino acid unit, bearing the hydroxamic acid linkage, present in ferrirhodin. The characterization of fusarinine has important implications for the biosynthesis of the ferrichrome group for it indicates that the hydroxamic acid bond is inserted at the free amino, acid, rather than at the peptide level. 

The biogenesis of the N-hydroxyamide bond is an interesting problem 115). That it may involve oxidation of the a- or co-amine group of an amino acid to a hydroxylamine derivative (Scheme 14, path a) was observed in the biosynthesis of ferrichrome (5) 116), hadacidin (13) (25, 117) and aerobactin (8) 118). 

Initial Steps in the Biosynthesis of Ferrichrome Incorporation of 8-N-Hydroxyor-nithine and 5-N-Acetyl-5-N-hydroxyornithine. Biochemistry 5, 3694 (1966). 

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