Identification and isolation of a cytosolic proteolytic complex containing insulin degrading enzyme and the multicatalytic proteinase.

The insulin degrading enzyme (IDE) is the first recognized member of a new class of metalloproteinases. Studies on the purification and the properties of this enzyme have led to divergent results and conclusions from different laboratories. The present manuscript suggests that many of the divergent results may be due to the interaction of this enzyme with other proteins as part of a proteolytic complex. IDE co-isolates with the multicatalytic proteinase (MCP) during a wide variety of purification approaches including affinity chromatography and conventional purification approaches. Ion exchange chromatography will partially or completely separate IDE and MCP. The SDS-PAGE protein bands at various purification steps suggest the presence of a cytosolic proteolytic complex containing IDE, MCP and other unidentified components and raise the possibility of a functional interaction among these proteins.