Biomedical Engineering Reference
In-Depth Information
In Mucorales Blakesleea trispora , Mucor circinelloides and Phycomyces
blakesleeanus , β-carotene is the main carotenoid accumulated. In the
Ascomycetes Gibberella fujikuroi and Neurospora crassa the main carotenoids
are β-carotene and neuroporaxanthin, whereas in the Basidiomycetous
Xanthophyllomyces dendrorhous astaxanthin is the major carotenoid.
A high variability has been found in the amount of the carotenoids
produced by fungi depending on many environmental factors such as
culture conditions, light, some chemicals, sexual interactions, etc. (Avalos
and Cerdá-Olmedo 2004).
In this chapter we review the biosynthesis, genetics, regulation and
industrial production of the fungal carotenoids, with particular emphasis
on Phycomyces blakesleeanus , Mucor circinelloides and Blakeslea trispora , all of
them belonging to the order Mucorales.
CONCLUSION
Structure and Biosynthesis of Carotenoids
Synthesis of Isoprenoids
The carotenoid biosynthetic pathway is a derivation of the isoprenoid
biosynthetic pathway, with common fi rst steps for both routes (from
the formation of IPP to obtain GGPP). IPP synthesis in fungi occurs
through a metabolic pathway known as the mevalonate path. It has its
beginning in the acetyl-CoA. Three molecules of this compound are
converted through acetoacetyl-CoA into 3-hydroxy-3-methylglutaryl-CoA
(HMG-CoA), which is then converted to mevalonate through a reductase
(Goodwin and Lijinsky 1952). Subsequently three reactions occur, two
phosphorylations and a decarboxylation, which convert mevalonate to
isopentenyl pyrophosphate (IPP). This molecule of 5 carbon atoms is the
fi rst isoprene unit. One molecule of IPP together with another molecule
of its isomer DMAPP is condensed to give rise to a molecule of 10 carbon
atoms, geranilpyrophososphate (GPP).
The further sequential addition of two IPP molecules to the GPP leads
fi rst to a molecule of 15 carbon atoms known as farnesyl pyrophosphate
(FPP) and then to another of 20 carbon atoms known as geranylgeranyl
pyrophosphate (GGPP). The prenyltransferases are the enzymes responsible
for sequential introduction of IPP molecules in various substrates of the
route. Generally, these enzymes act on substrates of different lengths
[DMAPP (C 5 ), GPP (C 10 ) and FPP (C 15 )].
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