A cellulase enzyme fraction was separated from Trichoderma reesei Pulpzyme HA(TM), and its characteristics suggested that it was mainly composed of cellobiohydrolase II (CBH II). The covalent attachment of pentaammineruthenium(III) to this enzyme resulted in threefold and fourfold enhancements of its hydrolytic activity on carboxymethyl cellulose (CMC) and barley beta-glucan, respectively, as well as endowing it with veratryl alcohol-oxidase activity. Enhancement of hydrolysis was not affected by addition of tartrate or hydrogen peroxide to the reaction mixture. Both native and pentaammineruthenium-modified enzymes had negligible activity on cellobiose and p-nitrophenyl beta-cellobioside (PNPC).