Activity of fungal β-glucosidases on cellulose

Malene B. Keller, Trine H. Sørensen, Kristian B.R.M. Krogh, Mark Wogulis, Kim Borch, Peter Westh*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

Abstract

Background: Fungal beta-glucosidases (BGs) from glucoside hydrolase family 3 (GH3) are industrially important enzymes, which convert cellooligosaccharides into glucose; the end product of the cellulolytic process. They are highly active against the β-1,4 glycosidic bond in soluble substrates but typically reported to be inactive against insoluble cellulose. Results: We studied the activity of four fungal GH3 BGs on cellulose and found significant activity. At low temperatures (10 °C), we derived the approximate kinetic parameters k cat = 0.3 ± 0.1 s-1 and K M = 80 ± 30 g/l for a BG from Aspergillus fumigatus (AfBG) acting on Avicel. Interestingly, this maximal turnover is higher than reported values for typical cellobiohydrolases (CBH) at this temperature and comparable to those of endoglucanases (EG). The specificity constant of AfGB on Avicel was only moderately lowered compared to values for EGs and CBHs. Conclusions: Overall these observations suggest a significant promiscuous side activity of the investigated GH3 BGs on insoluble cellulose. This challenges the traditional definition of a BG and supports suggestions that functional classes of cellulolytic enzymes may represent a continuum of overlapping modes of action.

Original languageEnglish
Article number121
JournalBiotechnology for Biofuels
Volume13
Issue number1
ISSN1754-6834
DOIs
Publication statusPublished - 10 Jul 2020

Bibliographical note

Funding Information:
This study was funded by the Novo Nordisk Foundation (Grant Numbers: NNF15OC0016606 and NNFSA170028392), the Innovation Fund, Denmark (Grant Numbers: 7043-00016B and 5150‐00020B), and the Carlsberg Foundation.

Keywords

  • Beta-glucosidases (BG)
  • Cellulose
  • Enzyme specificity
  • Glucoside Hydrolase Family 3 (GH3)

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