Purification and characterization of a thermostable glucoamylase from a Myrothecium isolate

Two glucoamylases, gluc I and gluc II, were purified to homogeneity from the culture filtrate of a Myrothecium strain M1 by chromatography on DEAE‐cellulose and concanavalin A‐sepharose. Molecular masses deduced by SDS‐PAGE were 72000 ± 2500 for gluc I and 96 000 ± 4000 for glue II. The temperature optima of the enzymes were both about 70°C and their pH optima were around 4.0. Both enzymes were glycoprotein and preferentially hydrolysed high molecular mass substrates. Hg 2+ was a potent inhibitor of both glucoamylases. Glue II had higher debranching activity than gluc I.