Characterization of a novel AA3_1 xylooligosaccharide dehydrogenase from Thermothelomyces myriococcoides CBS 398.93

Hongbo Zhao*, Johanna Karppi, Thi Truc Minh Nguyen, Annie Bellemare, Adrian Tsang, Emma Master, Maija Tenkanen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)
52 Downloads (Pure)


Background: The Carbohydrate-Active enZymes (CAZy) auxiliary activity family 3 (AA3) comprises flavin adenine dinucleotide-dependent (FAD) oxidoreductases from the glucose–methanol–choline (GMC) family, which play auxiliary roles in lignocellulose conversion. The AA3 subfamily 1 predominantly consists of cellobiose dehydrogenases (CDHs) that typically comprise a dehydrogenase domain, a cytochrome domain, and a carbohydrate-binding module from family 1 (CBM1). Results: In this work, an AA3_1 gene from T. myriococcoides CBS 398.93 encoding only a GMC dehydrogenase domain was expressed in Aspergillus niger. Like previously characterized CDHs, this enzyme (TmXdhA) predominantly accepts linear saccharides with β-(1 → 4) linkage and targets the hydroxyl on the reducing anomeric carbon. TmXdhA was distinguished, however, by its preferential activity towards xylooligosaccharides over cellooligosaccharides. Amino acid sequence analysis showed that TmXdhA possesses a glutamine at the substrate-binding site rather than a threonine or serine that occupies this position in previously characterized CDHs, and structural models suggest the glutamine in TmXdhA could facilitate binding to pentose sugars. Conclusions: The biochemical analysis of TmXdhA revealed a catalytic preference for xylooligosaccharide substrates. The modeled structure of TmXdhA provides a reference for the screening of oxidoreductases targeting xylooligosaccharides. We anticipate TmXdhA to be a good candidate for the conversion of xylooligosaccharides to added-value chemicals by its exceptional catalytic ability.

Original languageEnglish
Article number135
Number of pages17
JournalBiotechnology for Biofuels and Bioproducts
Issue number1
Publication statusPublished - 7 Dec 2022
MoE publication typeA1 Journal article-refereed


  • AA3_1
  • CAZy AA3
  • Cellobiose dehydrogenase
  • Thermothelomyces myriococcoides
  • Xylooligosaccharide dehydrogenase


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