Trihydroxamate siderophores

Jalal MAF, Love SK, van der Hehn D (1988) A -Dhnethylcoprogens. Three Novel Trihydroxamate Siderophores from Pathogenic Fungi. Biol Metals 1 4... 

Jalal, M. A. F., Love, S. K., and van der Helm, D. (1988). Af -Dimethylcoprogens. Three novel trihydroxamate siderophores from pathogenic fungi. Biol. Met. 1,4-8. 

Figure 38 5 Short term Fe uptake rates from model iron/ligand complexes hy Trichodesmium colonies collected in the suhtropical Atlantic Ocean. Shown are uptake rates from Fe complexed to a trihydroxamate siderophore (desferrioxamine), a dihydroxamate siderophore (rhodoturulic acid), and a porphyrin (protoporphyrin IX). For comparative purposes, uptake rates were also measured using added inorganic Fe (111). Achilles et al. (2003), Limnology and Oceanography 48 2250-2255.

Cocozza C., Tsao C. C. G., Cheah S.-F., Kraemer S. M., Raymond K. N., Miano T. M., and Sposito G. (2002) Temperature dependence of goethite dissolution promoted by trihydroxamate siderophores. Geochim. Cosmochim. Acta 66, 431-438. 

The ferrichromes, fusarinines, and ferrioxamines are typical trihydroxamate siderophores, while enterobactin is a cyclic tricatecholate siderophore. However, there are several exceptions which employ mixed forms of coordination. For example, aero-bactin, schizokinen and arthrobactin contain, in addition to two hydroxamate groups, a a-hydroxy-carboxylate unit which completes the hexadentate ligand structure 30). The recently isolated ferrioxamine H, with two hydroxamate and one carboxylate, is only pentadentate — the sixth coordination site presumably occupied by water 31). 

In view of the several assumptions, such as the lack of a precise number for the extinction of ferric agrobactin, an exactly quantitative value cannot be placed on the affinity of agrobactin for ferric ion. However it is clear that the binding strength is comparable to that of enterobactin, which at pH 7. + is reported (I8) to have a formation constant 10 -larger than ferrichrome, a cyclohexapeptide trihydroxamate siderophore with a... 

In order to introduce three chelating chains on the lower rim of calix[4]arenes, two general methodologies have been developed for the selective synthesis of calix[4]arene monoalkyl ethers [22]. The synthesis of trihydroxamate siderophores was achieved through the sequence of reactions reported in Scheme 1. The convergence of the three chelating chains was established by and NMR [23]. The pKa values of compound 10 were evaluated in ethanol/water 9 1 the first proton dissociation constant... 

Siderophores are iron-complexing compounds of low molecular weight that are synthesized by bacteria and fungi, and serve to deliver iron to the microbes. Because of their exclusive affinity and specificity for Fe3+, natural siderophores and synthetic derivatives have been exploited in the treatment of human iron-overload diseases. The most successfully used example is Desferal , which is the methane sulfonate derivative of iron-free ferrioxamine B, a linear trihydroxamate (Figure 3.2). Ferrioxamine was isolated in 1958 from the culture supernatant of Streptomyces... 

The ferrioxamines are a family of linear and cyclic siderophores built up from l-amino-5-(hydroxyamino)alkanes and succinic and acetic acids. Figure 47 shows ferrioxamine B, a linear trihydroxamic acid, which is probably the best-known example. The mesylate salt of the deferri form of ferrioxamine B is used in the clinical treatment of iron-overloaded patients. 

The second main class of Fem-specific sequestering agents (siderophores) responsible for the acquisition and assimilation of iron employ hydroxamate ligating groups (34).157158 186 Two important subclasses are the ferrioxamines and the ferrichromes (Figure 5). Examples are ferrioxamine B, a linear trihydroxamic acid and ferrichrome A, a cyclic hexapeptide carrying three hydroxamate-containing side chains. 

Iron(III) trihydroxamates related to the F. are ferricro-cin, ferrichrysin, ferrirhodin and ferrinibin (see formula). Other iron-transporting compounds from fungi are fusigen, caprogen, rhodotorulic acid, and, with regard to type, the new polycarboxylate siderophores (e. g rhizoferrin). 

Sifleramines. Obsolete name for microbial iron(III) complexes of the trihydroxamate type with growth promoting properties (e.g., ferrioxamines, ferri-chromes). Tlie name siderophores is now established for the low-molecular weight compounds participating in iron transport. 

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