7
(Fig. 1.3). The moieties are connected through a peptide or ester bond to form hexadentate structures with improved affinity for ferric form of iron. An iron-chelating
hydroxamate, hexadehydroastechrome, from A. fumigatus is less known and needs
to be tested further for its utility (Renshaw et al. 2002; Armstrong and Baalen 1979).
Even though siderophores are synthesized from different structural families,
most of the siderophores produced by a single organism is limited to a specific
structural family. Mucorales synthesizes rhizoferrin and Penicillium bilaii synthesizes catecholate pistillarin which are polycarboxylates. The chemical stability is
enhanced with the cyclization of siderophore, which is evident with a few fusarinines and most of ferrichromes. Similar to Rhodotorula spp., basidomycetous yeasts
produce rhodotorulic acid that contains two N-acetyl-N-hydroxy-1-ornithine connected together as a diketopiperazine nucleus. The fusarinines are formed from the
three N-cis-anhydromevalonyl-N hydroxy-l-ornithine units that are connected by
the ester bonds. The coprogens containing three units of N-trans-anhydromevalonylN-hydroxy-l-ornithine are formed from trans-fusarine units. Among these, two
units are linked together to form diketopiperazine ring, and the third unit forms ester
with the OH group of diketopiperazine ring at the C-terminal. The organic reactions
such as N-acetylation and N-methylation are responsible for the varieties within the
coprogens family (Renshaw et al. 2002; An et al. 1997a, b). Epichloë festucae, an
endophyte, produces a siderophore of ferrichrome variety that has a novel structure.
The epichloënin A siderophore structure contains tetra-glycines, single glutamine,
and three N-trans anhydromevalonyl-N-hydroxy-l-ornithine groups (Renshaw et al.
2002; Armstrong and Baalen 1979; An et al. 1997a, b).
H
H
H
N
N
O
O
OH
O
H 2 N
OH
O
O
H 2 N
HO
OH
HN
N
H
H
L-ornithine
Hydroxylation
Acylation
N
5 Hydroxy ornithine
Hydroxymate siderophore
Fig. 1.3 Biosynthesis of hydroxamate siderophore
1 Basics of Fungal Siderophores: Classification, Iron Transport and Storage…
(Fig. 1.3). The moieties are connected through a peptide or ester bond to form hexadentate structures with improved affinity for ferric form of iron. An iron-chelating
hydroxamate, hexadehydroastechrome, from A. fumigatus is less known and needs
to be tested further for its utility (Renshaw et al. 2002; Armstrong and Baalen 1979).
Even though siderophores are synthesized from different structural families,
most of the siderophores produced by a single organism is limited to a specific
structural family. Mucorales synthesizes rhizoferrin and Penicillium bilaii synthesizes catecholate pistillarin which are polycarboxylates. The chemical stability is
enhanced with the cyclization of siderophore, which is evident with a few fusarinines and most of ferrichromes. Similar to Rhodotorula spp., basidomycetous yeasts
produce rhodotorulic acid that contains two N-acetyl-N-hydroxy-1-ornithine connected together as a diketopiperazine nucleus. The fusarinines are formed from the
three N-cis-anhydromevalonyl-N hydroxy-l-ornithine units that are connected by
the ester bonds. The coprogens containing three units of N-trans-anhydromevalonylN-hydroxy-l-ornithine are formed from trans-fusarine units. Among these, two
units are linked together to form diketopiperazine ring, and the third unit forms ester
with the OH group of diketopiperazine ring at the C-terminal. The organic reactions
such as N-acetylation and N-methylation are responsible for the varieties within the
coprogens family (Renshaw et al. 2002; An et al. 1997a, b). Epichloë festucae, an
endophyte, produces a siderophore of ferrichrome variety that has a novel structure.
The epichloënin A siderophore structure contains tetra-glycines, single glutamine,
and three N-trans anhydromevalonyl-N-hydroxy-l-ornithine groups (Renshaw et al.
2002; Armstrong and Baalen 1979; An et al. 1997a, b).
H
H
H
N
N
O
O
OH
O
H 2 N
OH
O
O
H 2 N
HO
OH
HN
N
H
H
L-ornithine
Hydroxylation
Acylation
N
5 Hydroxy ornithine
Hydroxymate siderophore
Fig. 1.3 Biosynthesis of hydroxamate siderophore
1 Basics of Fungal Siderophores: Classification, Iron Transport and Storage…