Induction of extracellular arabinases on monomeric substrates in Aspergillus niger.
The induction of extracellular arabinases by pentose sugars and polyols generated by the metabolic pathway of L-arabinose and D-xylose catabolism in Aspergillus niger was investigated. Induction occurred with L-arabinose and L-arabitol but not with D-xylose or xylitol. L-arabitol in particular was found to be a good inducer for alpha-L-arabinofuranosidase and endo-arabinase activities. Western blotting analysis showed both alpha-L-arabinofuranosidase A and B to be present. No induction was observed using D-arabitol. Unlike the wild type A. niger N402 strain, the A. niger xylulose kinase negative mutant N572 also showed induction of alpha-L-arabinofuranosidases A and B and endo-arabinase activity on D-xylose and xylitol. This is due to metabolic conversion of these compounds leading to the accumulation of both xylitol and L-arabitol in this mutant, the latter of which then acts as inducer. The induction of the two alpha-L-arabinofuranosidases and endo-arabinase is under the control of two regulatory systems namely pathway specific induction and carbon catabolite repression. Under derepressing conditions in the wild type only alpha-L-arabinofuranosidase B could be detected by Western blotting analysis. This indicates that alpha-L-arabinofuranosidase B is of importance in the initiation of specific induction of the various arabinose activities in A. niger grown on arabinose containing structural polysaccharides.
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Department of Genetics, Agricultural University, Wageningen, The Netherlands.
Flipphi
M J
MJ
Voragen
A G
AG
Visser
J
J
D001086:Arabinofuranosyluracil / Q000096:biosynthesis* / Q000378:metabolism; D001089:Arabinose / Q000378:metabolism*; D001234:Aspergillus niger / Q000145:classification / Q000201:enzymology*; D004790:Enzyme Induction
D001086:Arabinofuranosyluracil; D001089:Arabinose