title: A novel L-xylulose reductase essential for L-arabinose catabolism in Trichoderma reesei.
abstract: L-Xylulose reductases belong to the superfamily of short chain dehydrogenases and reductases (SDRs) and catalyze the NAD(P)H-dependent reduction of L-xylulose to xylitol in L-arabinose and glucuronic acid catabolism. Here we report the identification of a novel L-xylulose reductase LXR3 in the fungus Trichoderma reesei by a bioinformatic approach in combination with a functional analysis. LXR3, a 31 kDa protein, catalyzes the reduction of L-xylulose to xylitol via NADPH and is also able to convert D-xylulose, D-ribulose, L-sorbose, and D-fructose to their corresponding polyols. Transcription of lxr3 is specifically induced by L-arabinose and L-arabitol. Deletion of lxr3 affects growth on L-arabinose and L-arabitol and reduces total NADPH-dependent LXR activity in cell free extracts. A phylogenetic analysis of known L-xylulose reductases shows that LXR3 is phylogenetically different from the Aspergillus niger L-xylulose reductase LxrA and, moreover, that all identified true L-xylulose reductases belong to different clades within the superfamily of SDRs. This indicates that the enzymes responsible for the reduction of L-xylulose in L-arabinose and glucuronic acid catabolic pathways have evolved independently and that even the fungal LXRs of the L-arabinose catabolic pathway have evolved in different clades of the superfamily of SDRs.
authors.affiliation: Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Metz
authors.forename: Dominik
authors.initials: D
authors.lastname: Mojzita
authors.forename: Silvia
authors.initials: S
authors.lastname: Herold
authors.forename: Christian P
authors.initials: CP
authors.lastname: Kubicek
authors.forename: Peter
authors.initials: P
authors.lastname: Richard
authors.forename: Bernhard
authors.initials: B
authors.lastname: Seiboth
mesh_terms: D001089:Arabinose / Q000378:metabolism*; D017353:Gene Deletion; D005800:Genes, Fungal; D010802:Phylogeny; D013401:Sugar Alcohol Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D014242:Trichoderma / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D014996:Xylulose / Q000378:metabolism
chemical_list: D014996:Xylulose; D001089:Arabinose; D013401:Sugar Alcohol Dehydrogenases; C023300:L-xylulose reductase