THE EFFECT OF XYLOGLUCANS ON THE DEGRADATION OF CELL-WALL-EMBEDDED CELLULOSE BY THE COMBINED ACTION OF CELLOBIOHYDROLASE AND ENDOGLUCANASESFROM TRICHODERMA-VIRIDE

Two endoglucanases of Trichoderma viride, endol and endolV, were assay ed for their activity toward alkali-extraded apple xyloglucans. EndolV was shown to have a 60-fold higher activity toward xyloglucan than en dol, whereas carboxymethyl cellulose and crystalline cellulose were be tter substrates for the latter. The enzymic degradation of cellulose e mbedded in the complex cell-wall matrix of apple fruit tissue has been studied using cellobiohydrolase (CBH) and these two different endoglu canases. A high-performance liquid chromatographic method (Aminex HPX- 22H) was used to monitor the release of cellobiose and oligomeric xylo glucan 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 endolV and CBH solubilized twice as much cellobiose co mpared to a combination of endol and CBH. Apparently, the concomitant removal of the xyloglucan coating from cellulose microfibrils by endol V 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-e mbedded cellulose by a three-enzyme system consisting of an endoglucan ase with high affinity toward cellulose (endol), a xyloglucanase (endo lV), and CBH.