Submitted to: Proceedings of the National Academy of Sciences(PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2009
Publication Date: 3/1/2009
Citation: Zhanmin, F., Wagschal, K.C., Wei, C., Montross, M., Lee, C.C., Yuan, L. 2009. Multimeric hemicellulases facilitate biomass conversion. Proceedings of the National Academy of Sciences. 75(6):1754-1757.
Interpretive Summary: Hemicellulose is a major component of the woody part of plants, and represents a significant renewable source of chemical energy. However, it would first be desirable to break the hemicellulose down into simpler components, that could be converted by other processes to a more useable form of the energy, e.g. bioethanol. Hemicellulose is structurally complex, and to enzymatically degrade it requires a suite of different enzymes. Three of the most important enzyme activities required for its degradation are xylanase, xylosidase, and arabinofuranosidase. We have taken the novel approach here of making two chimeric trifunctional enzymes with the aforementioned actoivities as well as integral carbohydrate binding domains. This approach can lower enzyme production costs, and moreover allows for synergetic action of the individual activities. Our results demonstrate the feasibility and advantages of generating trifunctional enzymes with itegral carbohydrate binding domains for the improvement of enzymatic hemicellulose degradation.
Technical Abstract: Two highly active trifunctional hemicellulases were constructed by linking the catalytic portion of a xylanase, an arabinofuranosidase and a xylosidase using either flexible peptide linkers or linkers containing a cellulose-binding domain (CBD). Both trimeric enzymes were produced in E. coli at high levels despite their relatively large sizes and showed similar pH, temperature optima and kinetics when compared to the parental enzymes. The trimeric enzymes are equally active as the parental-enzyme mixture in degradation of wheat or rye arabinoxylans. The CBD-containing trimeric enzyme is more active than the non-CBD trimeric enzyme or the parental-enzyme mixture in corn stover hydrolysis both in the presence or absence of cellulases. Our results demonstrate the feasibility and advantages of generating multifunctional enzymes for the improvement of biomass depolymerization.