[Cell envelope-bound proteinase activities of Acinetobacter calcoaceticus]

Acinetobacter calcoaceticus contains proteolytic activity after growth on various culture media. The enzyme activity could be found in the cytosolic fraction as well as in the cell envelopes (also containing the intracytoplasmic membranes). The highest proteolytic activity could be detected during the transition from the logarithmic growth phase to the stationary phase and in the early stationary phase, respectively. In the culture medium proteolytic activity was only evident in the later stationary phase. This activity was very instable and was liberated apparently by autolysis of the cells. The concentration of the nitrogen source (NH4+) in the medium (i.g. with acetate as carbon source) influences the proteinase activities of the cells. When nitrogen is limited, the proteolytic activity increases strongly in the stationary phase. The pH-profile of the azocaseinolytic activities of the cytosol was nearly the same as that of the cell envelopes (pH-optima are between 7 and 9). A partial inhibition of the proteolytic activities in the cytosol as well as in the cell envelopes could be attained by serine proteinase inhibitors. Inhibitors of thiol- and metalloproteinases showed no effects.