Enzymatic polymerization catalyzed by immobilized endoglucanase on gold.

ABSTRACT

Enzymatic polymerization was carried out on gold by immobilized genetically engineered endoglucanase II (EGII) from Trichoderma viride , and the polymerization behavior and the produced cellulose were analyzed in comparison with those by free enzymes. Mutant EGIIs were EGII(core2) and EGII(core2H), which consist of two sequential catalytic core domains with one His-tag (His6) on N-terminal and with totally two His-tags on both terminals, respectively. His-tagged EGIIs were immobilized via Ni chelators of nitrilotriacetic acid (NTA) introduced on gold surface. From SPR measurements, the affinity of EGII(core2H) to the surface was higher than that of EGII(core2), and the molecular occupation area of EGII(core2H) was larger than that of EGII(core2), indicating that EGII(core2H) was immobilized with utilizing two His-tags introduced on both terminals. The hydrolytic activity of the immobilized EGII(core2H) using cellohexaose as substrate was slightly lower than that of free EGII(core2H) when they were compared at the same amount in the hydrolytic system. Enzymatic polymerization catalyzed by both immobilized EGII(core2) and EGII(core2H) proceeded with producing highly crystalline cellulose in comparison with free enzyme. Immobilization of the endoglucanase is thus effective to obtain crystalline cellulose due to the high density of the catalytic domain on gold.