Characterization of a periplasmic insulin-cleaving metalloproteinase from Acinetobacter calcoaceticus

In Acinetobacter calcoaceticus, a Gram-negative bacterial species, a soluble insulin-degrading proteinase, located in the periplasm as well as in the cytosol, could be established. The periplasmic and cytosolic enzymes agree in their inhibition pattern, pH-optimum and molecular weight. The insulin-degrading enzyme of Acinetobacter calcoaceticus resembles the corresponding proteinases of Escherichia coli. It is a metalloproteinase with a pH-optimum in the neutral range and can be reactivated by divalent ions after EDTA-inhibition, but it is not entirely identical with any of the described proteinases of Escherichia coli in its inhibitory behaviour.