beta-Xylosidase activity, encoded by xlnD, is essential for complete hydrolysis of xylan by Aspergillus niger but not for induction of the xylanolytic enzyme spectrum

Eur J Biochem. 1997 Apr 1;245(1):164-73. doi: 10.1111/j.1432-1033.1997.00164.x.


Two proteins exhibiting beta-D-xylosidase activity were identified upon fractionation and purification of a culture filtrate of an arabinoxylan-grown Aspergillus niger. A single band of 110 kDa by SDS/PAGE was obtained in both cases and these were active on xylo-oligosaccharides and on xylan. Partial xlnD cDNA clones were immunochemically identified and isolated from a lambda cDNA expression library. Sequence analysis showed that all cDNA clones correspond to a single gene. A genomic clone was isolated and overexpressed in A. niger and A. nidulans. The xlnD gene has an ORF of 2412 nucleotides, encodes a protein of 804 amino acids and contains a potential signal peptide of 26 amino acids. This results in a mature protein of 778 amino acids with a predicted molecular mass of 85 kDa and an isoelectric point of 4.5. The protein is N-glycosylated and contains 15 potential N-glycosylation sites. Sequence similarity is found with beta-D-glucosidases both of bacterial and fungal origin. Both beta-xylosidase proteins purified have high activity on the artificial substrate p-nitrophenyl beta-D-xylopyranoside (XylNp) and a side activity on p-nitrophenyl alpha-L-arabinofuranoside and p-nitrophenyl beta-D-glucopyranoside. A niger strains in which the xlnD gene was disrupted accumulate mainly xylobiose and xylotriose when grown on xylan and have no significant beta-xylosidase activity in the culture medium, indicating that this gene encodes the major extracellular beta-xylosidase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Aspergillus niger / enzymology*
  • Aspergillus niger / genetics
  • Base Sequence
  • Cloning, Molecular
  • DNA, Fungal / chemistry
  • Enzyme Induction
  • Molecular Sequence Data
  • Xylans / metabolism*
  • Xylosidases / genetics
  • Xylosidases / metabolism*


  • DNA, Fungal
  • Xylans
  • Xylosidases
  • exo-1,4-beta-D-xylosidase

Associated data

  • GENBANK/B49776
  • GENBANK/L06134
  • GENBANK/U09580
  • GENBANK/U24701
  • GENBANK/X96734
  • GENBANK/Z56279
  • GENBANK/Z84377
  • SWISSPROT/P06835
  • SWISSPROT/P07337
  • SWISSPROT/P14002
  • SWISSPROT/P22506
  • SWISSPROT/P22507
  • SWISSPROT/P27034
  • SWISSPROT/P29090
  • SWISSPROT/P33363
  • SWISSPROT/P48825