Transglycosylation Activities of Exo- and Endo-Type Cellulases from Irpex lacteus (Polyporus tulipiferae)

Two highly purified cellulases, Ex-1 [ exo-type, exo-cellobiohydrolase, EC 3.2.1.91] and En-1 [endo-type, EC 3.2.1.4] obtained from Driselase, a commercial enzyme preparation from Irpex lacteus (Polyporus tulipiferae), were used in this work. Both cellulases produced ¹⁴C-cellooligosaccharides such as ¹⁴C-G₂ and ¹⁴C-G₃ by transglycosylation when G₃, G₅ or β-PNPC was used as a donor and ¹⁴C-G₁ as an acceptor. However, the transglycosylation activity of Ex-1 was far higher than that of En-1.

When Ex-1 or En-1 was incubated with β-PNPG only, no p-nitrophenol was released, but it was readily released when G₃ was added to the reaction mixture. In this reaction, the optimal donor (G₃) concentration for Ex-1 was 1.0 mM and the optimal pH values of Ex-1 were at 2.7 and 3.7 for β-PNPG and β-PG as acceptors, respectively, these values being far lower than the ordinary optimal pH values of the cellulase (4.0–5.0).