title: Fungal arabinan and L-arabinose metabolism.
abstract: L-Arabinose is the second most abundant pentose beside D-xylose and is found in the plant polysaccharides, hemicellulose and pectin. The need to find renewable carbon and energy sources has accelerated research to investigate the potential of L-arabinose for the development and production of biofuels and other bioproducts. Fungi produce a number of extracellular arabinanases, including α-L-arabinofuranosidases and endo-arabinanases, to specifically release L-arabinose from the plant polymers. Following uptake of L-arabinose, its intracellular catabolism follows a four-step alternating reduction and oxidation path, which is concluded by a phosphorylation, resulting in D-xylulose 5-phosphate, an intermediate of the pentose phosphate pathway. The genes and encoding enzymes L-arabinose reductase, L-arabinitol dehydrogenase, L-xylulose reductase, xylitol dehydrogenase, and xylulokinase of this pathway were mainly characterized in the two biotechnological important fungi Aspergillus niger and Trichoderma reesei. Analysis of the components of the L-arabinose pathway revealed a number of specific adaptations in the enzymatic and regulatory machinery towards the utilization of L-arabinose. Further genetic and biochemical analysis provided evidence that L-arabinose and the interconnected D-xylose pathway are also involved in the oxidoreductive degradation of the hexose D-galactose.
authors.affiliation: Research Area Gene Technology and Applied Biochemistry, Institute of Chemical Engineering, Vienna University of Technology, Wien, Austria. bseiboth@mail.tuwien.ac.at
authors.forename: Bernhard
authors.initials: B
authors.lastname: Seiboth
authors.forename: Benjamin
authors.initials: B
authors.lastname: Metz
mesh_terms: D001089:Arabinose / Q000378:metabolism*; D001234:Aspergillus niger / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D011134:Polysaccharides / Q000378:metabolism*; D014242:Trichoderma / Q000378:metabolism*
chemical_list: D011134:Polysaccharides; C030080:araban; D001089:Arabinose