Evolutionary molecular engineering and structure-activity relationship in cellulase condensation reaction.

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Endoglucanase I(EG I) from filamentous fungus Trichoderma reesei has not been considered to hydrolyze the"cellobiose". On the other hand, the physiological role of a secretedβ-glucosidase I(BGL I) is not clear, which can hydrolyze cellobiose outside fungus body. T. reesei derived EG I, of which catalytic domain was used, generated glucose(product) from cellobiose(substrate) in a substrate concentration-dependent manner, and glucose production ratio reached to more than half of BGL I under the high substrate concentration such as 1 M. When T. reesei derived BGL I reacted with a high concentration of cellobiose, a remarkable synthesis of trisaccharide considered as transglycosylational product was observed. In the case that BGL I reacts with high concentrations of glucose, no condensational product was observed. The physiological role of BGL I is considered to be different to BGL II in the fungus body, which has been reported to generate the strongest cellulase inducer sophorose by the in vitro condensation of high concentration of glucose.