The d‐xylose reductase of Hypocrea jecorina is the major aldose reductase in pentose and d‐galactose catabolism and necessary for β‐galactosidase and cellulase induction by lactose

l-xylo-3-Hexulose Reductase Is the Missing Link in the Oxidoreductive Pathway for d-Galactose Catabolism in Filamentous Fungi

“…However, in this case, T. reesei also uses two different enzymes, LXR4 for the L-xylo-3-hexulose reduction and LXR3 for the L-xylulose reduction. 6 The LXR4 has the closest sequence similarity of the A. niger enzymes LxrA and XhrA in T. reesei. The LXR3, however, is more distant in terms of sequence similarity (supplemental Fig.…”

“…Another candidate LXR3 (GenBank accession number BK008567), which was identified and characterized as a gene encoding the true L-xylulose reductase of T. reesei, showed only activity with L-xylulose but not with L-xylo-3-hexulose in vitro. 6 Moreover, none of these genes are close homologues of xhrA. By searching the T. reesei genome, we identified a gene that we called lxr4 (GenBank accession number BK008566) as the closest orthologue for lxrA.…”

“…In T. reesei, the first and second steps of both pathways are catalyzed by the same enzymes. The T. reesei XYL1 is the major enzyme for L-arabinose and D-galactose reduction (6), and LAD1 is the main enzyme for galactitol and L-arabitol oxidation (9,10). In A. niger, close homologues of different enzymes are used; XyrA is used for D-galactose reduction, and LarA is used for L-arabinose reduction (7).…”

“…Because galactitol accumulated in this strain, it was suggested that a pathway exists in T. reesei where D-galactose is reduced in the first step (5). In T. reesei, an aldose reductase, XYL1, was shown to be responsible for the reduction of D-galactose to galactitol as well as for the reduction of D-xylose and L-arabinose (6). A. niger has distinct L-arabinose and D-xylose reductases, LarA and XyrA (7).…”

Global nutrient profiling by Phenotype MicroArrays: a tool complementing genomic and proteomic studies in conidial fungi

“…Since cellulase formation is triggered by sporulation (Kubicek, 1987), γ-aminobutyrate may constitute a link between cellulase induction and conidiation. On the other hand, the increased utilization of D-sorbitol by the improved producer strain QM 9414 may be linked to enhanced formation of L-sorbose, an inducer of cellulase formation in H. jecorina (Nogawa et al, 2001), because it is formed from D-sorbitol by the respective nicotinamide adenine dinucleotide phosphate (NADP)-dependent ketose reductase (Seiboth et al, 2007). While the importance of these two findings for cellulase production must be verified by reverse genetics, they have nevertheless pointed to two biochemical reactions, which may have a major impact on cellulase formation, and would have remained undetected without PM analysis.…”