Siderophores synthesis

Bacterial siderophores are typically small peptidic molecules, which contain side chains and functional groups that can provide high-affinity ligands for coordination of ferric ions. The structures of some siderophores are shown in Drechsel and Jung [142]. Siderophore synthesis occurs via enzymatic assembly by nonribosomal peptide synthetases [144], In bacteria, siderophore synthesis is... 

Visca P, Colotti G, Serino L, Verzili D, Orsi N, Chiancone E (1992) Metal Regulation of Siderophore Synthesis in Pseudomonas aeruginosa and Functional Effects of Siderophore-Metal Complexes. Appl Environ Microbiol 58 2886... 

Bartholdy BA etal, Hydroxamate siderophore synthesis hy Phialocephalafortinii, a typical dark septate fungal root endophyte, BioMetals 14 33-42, 2001. 

S.P. Sweet and L.J. Douglas, Effect of iron concentration of siderophore synthesis and pigment production by Candida albicans, FEMS Microbiol. Lett., 80, 87, 1991. 

The competition between transferrin and infectious organisms is a fascinating topic. During infection, the mammalian host will attempt to diminish the iron available to the bacterium. The iron levels in the blood decrease and the iron stores in the liver increase. The observation that siderophore synthesis is sharply reduced at temperatures just over 37 °C may mean that the physiological function of fever is to depress bacterial siderophore synthesis, as shown for a rabbit pathogen, Pseudomonas multocida.1203... 

Macrocyclic lactones as microbial siderophores, synthesis and structure in solution 84CRV587. 

For bacteria to continue to multiply in the blood, they must synthesize new supplies of siderophores. Synthesis of siderophores in bacteria slows, however, as the temperature is increased above the normal body temperature of 37 °C and stops completely at 40 °C. This suggests that fever in the presence of an invading microbe is a mechanism used by the body to deprive bacteria of iron. 

In response to iron deprivation, E. chrysanthemi induces the synthesis of siderophores and also the transcription of pectate lyase genes (52). The pelB, pelC, pelE and pelL genes are induced under Umited iron-deprivation whereas pelD is only induced under severe iron-deprivation (53). Iron sensing in E. 

During the synthesis of siderophores, the simultaneous removal of the benzyl, p-nitrobenzyl, and -butoxicarbonyl protecting groups was accomplished under acidic hydrogenolysis conditions (H2, 10% Pd/C in DMF-HC1-H20). 

The ent-fes-fep gene cluster is necessary for the synthesis of enterobactin and transport of the iron loaded siderophore. The fes gene product was shown to be necessary for utilization of the siderophore-bound iron inside the cell. The protein has an esterase activity which cleaves the ester bonds of the cyclic 2,3-dihydroxybenzoylserine ester in enterobactin. However, the esterase activity of Fes does not seem to be important for iron mobilization since Fes is also necessary for the utilization of iron from enterobactin analogues which do not have ester bonds (Heidinger et ah, 1983). No reductase activity has been found in Fes (Brickman and McIntosh, 1992) or in any other protein encoded in the ent-fes-fep gene cluster. 

Transferrin iron uptake via receptor-mediated endocytosis has clearly appeared fairly late in evolution, when we consider that the bilobal iron-binding protein is found only as far back as insects . As we have seen in the preceding chapters, iron-uptake mechanisms involving the synthesis of more or less specific siderophores have evolved together with strategies implying the solubilization of insoluble ferric iron by the combined effects of pH and reduction, and even the development of receptor proteins capable of taking up transferrin-, lactoferrin- or haem-bound iron from specific hosts. 

The terephthalamide moiety (Fig. 13) is similar in structure to catechol, but has a higher affinity for iron(III) at physiological conditions and consequently has been used in the synthesis of siderophore mimics. The higher pFe values are due to the... 

Pistillarin was first isolated from Clavariadelphus pistillaris and from several Ramaria spp. (Basidiomycetes) 334). Recently, it was found to be produced also by the marine fungus Penicillium bilaii 56). Like siderochrome II below it is a spermidine derivative substimted only at the terminal NHa-groups (A, iV °-di-(3,4-dihydroxy)benzoyl-spermidine). Its synthesis and that of siderochrome II was reported, their siderophore activity and their complexation with Fe (1 1 complexes) was investigated 102, 299). A derivative of pistillarin substituted at aU three amino functions has not been reported yet. 

Naimochelin C (Fig. 15, 54) from the myxobacterium Nannocystis exedens contains two L-Lys and two ( )-cinnamic acid units. The reported mono- and di-methyl esters (nannochelin B and A) may be artifacts from the work-up (198). A synthesis is described (29) (see Sect. 8.4). The ochrobactins (Fig. 15,55) isolated from the sea-shore bacterium Ochrobactrum sp. (214) with the spacer L-lysine are membrane active due to the fatty acid residues (saturated Cg and (2 )-unsaturated Cg and Cio) cf. lipopeptidic siderophores in Sect. 2.8. 

Rhizobactin 1021 (Fig. 15, 56) (for rhizobactin, see diaminoalkane-based siderophores, Sect. 3.1) from Rhizobium meliloti (281), contains an acetyl and an ( )-decenoyl group. Its Fe " complex in aqueous solution is A-configured and forms an equilibrium between a monomeric and a dimeric form that can be separated by chromatography. A synthesis is described (404). 

Micacocidin (Fig. 22, 68) from Pseudomonas sp. complexes Fe " and other metal ions 189,190). Whether it acts as a siderophore has not been investigated. A stereospecific synthesis was elaborated 161,161a), but the same isomerization problems at C-4 and C-2" were encountered as had been observed with pyochelin (see Note 14 in 161)). 

From iron-deficient cultures of Pseudomonas fluorescens, 8-hydroxy-4-methoxy-monothioquinaldic acid (thioquinolobactin) together with the corresponding quinaldic acid (quinolobactin) (Fig. 26, 74 and 75), could be isolated (258). Quinolobactin can act as an alternative siderophore of Pseudomonas fluorescens (245), although it is the hydrolysis product of the thioacid (220). Its synthesis and complex formation as (Fe )Lig2 was described (9S). 

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