Novel mutant enzymes of endoglucanase II (EGII) from fungus Trichoderma viride were prepared and their hydrolysis and enzymatic polymerization activities were studied. EGII((core)2) and EGII((core)2-His), which possess sequential two active sites of EGII with a His-tag probe at the N-terminal and with His-tag probes at the N and C terminals, respectively, showed higher hydrolysis activities than EGII(core) with a single active site even in comparison on the active-site concentration basis. These mutant enzymes were applied to the enzymatic polymerization to afford artificial cellulose. The polymerization rates with using EGII((core)2) and EGII((core)2-His) were also higher than that with using EGII(core).The polymerization products were identified as highly crystalline cellulose of type II. The mutant enzymes were also effective to prepare spherulites. EGII((core)2) and EGII((core)2-His) are considered to possess higher hydrolysis and polymerization activities than EGII(core) mainly due to the suitably stabilized conformation with the sequential arrangement. (C) 2008 Elsevier B.V. All rights reserved.