Implications of cellobiohydrolase glycosylation for use in biomass conversion |
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Authors: | Tina Jeoh William Michener Michael E Himmel Stephen R Decker William S Adney |
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Institution: | (1) Biological and Agricultural Engineering Department, University of California at Davis, Davis, California, USA;(2) National Renewable Energy Laboratory, National Bioenergy Center, 1617 Cole Blvd., Golden, CO 80401, USA;(3) National Renewable Energy Laboratory, Chemical and Biosciences Center, 1617 Cole Blvd., Golden, CO 80401, USA |
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Abstract: | The cellulase producing ascomycete, Trichoderma reesei (Hypocrea jecorina), is known to secrete a range of enzymes important for ethanol production from lignocellulosic biomass. It is also widely
used for the commercial scale production of industrial enzymes because of its ability to produce high titers of heterologous
proteins. During the secretion process, a number of post-translational events can occur, however, that impact protein function
and stability. Another ascomycete, Aspergillus niger var. awamori, is also known to produce large quantities of heterologous proteins for industry. In this study, T. reesei Cel7A, a cellobiohydrolase, was expressed in A. niger var. awamori and subjected to detailed biophysical characterization. The purified recombinant enzyme contains six times the amount of
N-linked glycan than the enzyme purified from a commercial T. reesei enzyme preparation. The activities of the two enzyme forms were compared using bacterial (microcrystalline) and phosphoric
acid swollen (amorphous) cellulose as substrates. This comparison suggested that the increased level of N-glycosylation of the recombinant Cel7A (rCel7A) resulted in reduced activity and increased non-productive binding on cellulose.
When treated with the N-glycosidase PNGaseF, the molecular weight of the recombinant enzyme approached that of the commercial enzyme and the activity
on cellulose was improved. |
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