Monday, April 29, 2013
Exhibit Hall
Cellobiohydrolases (CBHs) of CAZy family GH7 are important enzymes in the process of enzymatic saccharification of cellulose, and one of the most commonly used enzyme mixture components in industrial processes is the CBH1 (also called Cel7A) from Trichoderma reesei (the anamorph of Hypocrea jecorina). Several reports have shown that xylans and xylo-oligos can have negative effect on the performance of the cellulase mixtures. Recent studies have shown that both GH6 and GH7 CBHs can be inhibited by xylans and xylo-oligosaccharides 1,2, which can be released by physicochemical pretreatment of lignocellulose and be present during saccharification if the substrate is kept unwashed .
To obtain a better understanding of this inhibition at a molecular level, we have determined structures, using X-ray crystallography, of two different catalytically deficient T. reesei CBH1 variants in complex with xylo-oligosaccharides. These structures show how xylo-oligosaccharides and xylan might interact with the enzyme to inhibit its activity. Complementary enzymatic studies of the wild-type CBH1 show indication of mixed inhibition and not pure competitive inhibition.
(1) Baumann et al. Biotechnology for Biofuels 2011, 4:45; (2) Zhang and Viikari. Bioresource Technology 117 (2012) 286–291