The Effect of Xyloglucans on the Degradation of Cell-Wall-Embedded Cellulose by the Combined Action of Cellobiohydrolase and Endoglucanases from Trichoderma viride.
AUTOR(ES)
Vincken, J. P.
RESUMO
Two endoglucanases of Trichoderma viride, endoI and endoIV, were assayed for their activity toward alkali-extracted apple xyloglucans. EndoIV was shown to have a 60-fold higher activity toward xyloglucan than endoI, whereas carboxymethyl cellulose and crystalline cellulose were better substrates for the latter. The enzymic degradation of cellulose embedded in the complex cell-wall matrix of apple fruit tissue has been studied using cellobiohydrolase (CBH) and these two different endoglucanases. A high-performance liquid chromatographic method (Aminex HPX-22H) was used to monitor the release of cellobiose and oligomeric xyloglucan fragments. Synergistic action between CBH and endoglucanases on cell-wall-embedded cellulose was, with respect to their optimal ratio, slightly different from that reported for crystalline cellulose. The combination of endoIV and CBH solubilized twice as much cellobiose compared to a combination of endoI and CBH. Apparently, the concomitant removal of the xyloglucan coating from cellulose microfibrils by endoIV is essential for an efficient degradation of cellulose in a complex matrix. Cellulose degradation slightly enhanced the solubilization of xyloglucans. These results indicate optimal degradation of cell-wall-embedded cellulose by a three-enzyme system consisting of an endoglucanase with high affinity toward cellulose (endoI), a xyloglucanase (endoIV), and CBH.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=159167Documentos Relacionados
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