A thermostable extracellular glucoamylase from Thermomyces
lanuginosus in static culture was purified to SDS–PAGE homogeneity
by fractional ammonium sulphate precipitation, ion-exchange chromatography
on
DEAE–Toyopearl, Butyl–Toyopearl hydrophobic
interaction chromatography, gel filtration on Sephacryl S-300 and ion-exchange
chromatography on FPLC MonoQ. The molecular
weight of the enzyme, consisting of a single polypeptide, was estimated
to
be 72000 by SDS–PAGE. The glucoamylase exhibited
maximal activities at pH 5·0. The optimum temperature for the activity
was 70°C. The enzyme was thermostable at 60° with half-lives at
70°
of 20 min and 80° of about 6 min. The glucoamylase was a glycoprotein
with 11·4% carbohydrate content. The enzyme
hydrolysed soluble starch, amylose, amylopectin, dextrin, glycogen, maltotroise
and maltose. Starch was the best substrate.