Purification and characterization of an extracellular polygalacturonase from the thermophilic fungus, Thermomyces lanuginosus

A polygalacturonase was purified from the thermophilic fungus, Thermomyces lanuginosus to apparent homogeneity by ultrafiltration, acetone precipitation and ion-exchange chromatography. The enzyme was maximally active at pH 5.5 and 60 degrees C. The apparent K-M with potassium pectate was 0.67 mg/ml and the V-max was 7.2 x 10(5) mu mol/min/mg protein. The apparent molecular weight of the enzyme was 59 kDa and it contained approximately 10% carbohydrate. The enzyme was completely stable at room temperature (32 +/- 3 degrees C) and retained about 50% activity at 50 degrees C for 6 h. The zymogram of the purified enzyme revealed two activity bands, one of which was a major one. Polyclonal antibodies raised against the enzyme did not show any immunological relatedness with other mesophilic polygalacturonases.