Characterization of alpha-amylase and pullulanase activities of Clostridium thermohydrosulfuricum. Evidence for a novel thermostable amylase.

Thermostable extracellular alpha-amylase and pullulanase activities of Clostridium thermohydrosulfuricum E 101-69 were characterized in a crude enzyme preparation. The activities responded similarly to temperature and pH, with optima at 85-90 degrees C and pH 5.6. The activities were stable at 65 degrees C, but were inactivated gradually in an identical manner at higher temperatures in the absence of Ca2+ and substrate. Ca2+ stabilized both activities similarly at high temperatures. Ca2+ also stimulated both activities, whereas EDTA reversed this stimulation. The activities were similarly inactivated at pH extremes. The two activities distributed in the same way during isoelectric focusing. The results suggest that the two activities are properties of the same protein, representing a novel, thermostable, amylase.