Activity of fungal β-glucosidases on cellulose

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 ℃), 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.

CAZyme prediction in ascomycetous yeast genomes guides discovery of novel xylanolytic species with diverse capacities for hemicellulose hydrolysis

“…Moreover, the CAZyme heatmap indicated potential for cellulolytic activity in several species, but this was not observed in the growth studies for the soluble cellulose analog CMC or crystalline and insoluble Avicel. For efficient degradation of cellulose to glucose, endoglucanase, cellobiohydrolase, lytic polysaccharide monooxygenase and β-glucosidase activities are generally regarded as needed [ 50 – 53 ]. The inability of yeasts to grow on cellulose may be due to the absence of one or several of the enzyme families known to encode such enzymes, such as GH6 (totally absent in the 332 yeasts) and GH7 (only present in B. peoriensis ) and GH12 (only found in B. mokoenaii ).…”

Once upon a Time, There Was a Piece of Wood: Present Knowledge and Future Perspectives in Fungal Deterioration of Wooden Cultural Heritage in Terrestrial Ecosystems and Diagnostic Tools

“…EGs cut at unpredictable locations within the insoluble crystalline cellulose polysaccharide chain, yielding oligosaccharides of varying lengths generating new chain ends and creating an open site for the CBHs that cleaves cellulose to release cellobiose or cellulo-oligosaccharides. The last enzyme BGLs has the function of degrading cellobiose into glucose [52]. Cellulose degradation involves other enzymes such as polysaccharide monooxygenases (PMOs), copper-containing oxidases that work synergistically with other enzymes [53].…”

Biopolymer-Based Nanosystems: Potential Novel Carriers for Kidney Drug Delivery

“…Cellulose is by far the most abundant, most common, and renewable natural biopolymer, which is derived from wood, cotton, bacteria, and fungi [ 98 , 99 ]. Cellulose is a polysaccharide with a linear structure consisting of multiple D-glucose units linked by β-1,4 glycosidic bonds ( Figure 5 ) [ 100 ]. The cellulose molecular formula is (C 6 H 10 O 5 ) n .…”