Fungal L-xylulose reductases

01.11.2006 - 31.12.2010
Forschungsförderungsprojekt
A large number of filamentous fungi grow on dead or decaying plant material and contribute thus to the rapid turn-over of lignin and diverse polysaccharides including cellulose, hemicellulose and pectin. Hemicelluloses and pectins are heteropolysaccharides composed mainly of pentoses, hexoses, or sugar acids. Their primary structure depends on the source and can vary even between different tissues of a single plant. The pentose L-arabinose is one of the main components of both hemicelluloses and pectins. An L-arabinose catabolic pathway is therefore of importance for many microorganisms and has also an impact on microbial fermentations in which cheap plant biomass is converted into industrially useful products such as fine chemicals or enzymes. Fungi have developed a specific pathway for the catabolism of pentoses such as L-arabinose or D-xylose. Most of the genes involved in the L-arabinose pathway of filamentous fungi have recently been cloned and functionally characterized. L-xylulose reductase catalyzes the third step in this five step pathway by converting L-xylulose to xylitol. An L-xylulose reductase gene (lxr1) from the filamentous fungus Hypocrea jecorina (anamorph: Trichoderma reesei) was cloned previously but the role of this gene in the catabolism of L-arabinose has now been questioned by a number of recent findings. Based on our data this gene encodes rather for a D-mannitol 2-dehydrogenase which is linked to developmental processes such as sporulation and condiospore germination. Enzymes with L-xylulose reductase are in addition involved in a number of other processes including catabolism of D-galactose and cellulase induction. The present proposal therefore aims at the identification and characterization of these enzymes with L-xylulose reductase activity in H. jecorina and a characterization of their role in the different metabolic pathways including L-arabinose, D-galactose and D-mannitol metabolism. Our organism of choice for this study is the filamentous fungus H. jecorina, a saprophyte with a broad biotechnological application due to its excellent secretion capacity for different extracellular enzymes, some produced industrially on a technical scale for textile or food industry. Sequencing of the H. jecorina genome was recently completed and provides therefore an excellent basis for future research.

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Grant funds

  • FWF - Österr. Wissenschaftsfonds (National) Austrian Science Fund (FWF)

Forschungsschwerpunkte

  • Biological and Bioactive Materials: 100%

Schlagwörter

DeutschEnglisch
L-Arabinose StoffwechselL-arabinose metabolism
D-Galactose StoffwechselD-galactose metabolism
Zellulasencellulase
HemizellulasenHemicellulases
biotechnologyBiotechnologie

Publikationen