Purification and properties of an extracellular endoglucanase from Myceliophthora thermophila D-14 (ATCC 48104)

An extracellular endoglucanase (1,4-beta-glucanohydrolase, EC 3.2.1.4) produced by Myceliophthora thermophila D-14 (ATCC 48104) has been purified to homogeneity by ammonium sulphate precipitation and two consecutive ion-exchange chromatographic steps on DEAE-Sephadex A-50 columns. The enzyme was purified 13.8-fold and was homogeneous by analytical PAGE and SDS-PAGE. It has a high apparent Mr, of about 100,000. The pH and temperature optima for its activity were 4.8 and 65 degrees C respectively. The Km of the purified enzyme for CMC (sodium salt) was 3 mg ml-1. The enzyme displayed low activity toward salicin and p-nitrophenyl beta-D-glucoside. The activity was enhanced in the presence of Na+, K+ and Ca2+ but effectively inhibited by Hg2+, Fe2+, Mg2+, Cu2+ and NH4+. Inhibition studies indicated that the enzyme may be a metalloprotein and/or that it requires metal ions for its optimum activity.