<p>The enzymatic degradation of cellulose is an important process in nature. This thesis has focused on the degradation of cellulose by enzymes from two cellulose-degrading fungi, <i>Hypocrea jecorina</i> and <i>Phanerochaete chrysosporium</i>, including both the action of the individual enzymes and their synergistic interplay. </p><p>The end-preference of cellobiohydrolases on crystalline cellulose was studied. Cellobiohydrolases belonging to glycosyl hydrolase (GH) family 7 were found to hydrolyse cellulose processively, starting from the reducing end of the cellulose chain. End-labelled cellulose can serve as a tool for functional classification of cellulases.</p><p>The synergy mechanism between endoglucanases and cellobiohydrolases was studied using substrates with different physical properties derived from bacterial cellulose. A new mechanism for synergism between endo- and exoacting enzymes was proposed whereby endoglucanases, in addition to creating nicks in amorphous parts of cellulose, thereby making new starting-points for processively acting cellobiohydrolases, also “polish” the cellulose surface by removing shorter chains from cellulose surface.</p><p>A new small endoglucanase belonging to the GH12 family was isolated and characterised. The proposed role of this enzyme is to make the cellulose in wood more accessible to other cellulases.</p><p>Oxygen conversion by cellobiose dehydrogenase was studied. Hydrogen peroxide produced by cellobiose dehydrogenase can be decomposed even by traces of certain metal ions into a hydroxyl radical and a hydroxyl ion. As an example, reduced metal ions will be continuously regenerated by cellobiose dehydrogenase, which thus stimulates the degradation.</p><p>Interactions between GH7 family cellobiohydrolases and o-nitrophenyl cellobioside were studied by fluorescence spectroscopy and kinetic tests. o-nitrophenyl cellobioside was used as indicator ligand to determine the dissociation constants for cellobiose binding to catalytically inactive Cel7A mutants by displacement binding experiments.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-6888 |
| Date | January 2006 |
| Creators | Nutt, Anu |
| Publisher | Uppsala University, Department of Biochemistry, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 185 |
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