Characterization of an insulin degrading enzyme from cultured human lymphocytes.

An insulin degrading enzyme from cultured human lymphocytes, IM-9 cells, has been purified and characterized. The biochemical, enzymatic and immunological characteristics of this enzyme were all found to be similar to the characteristics of insulin degrading enzymes previously isolated from rat and pig skeletal muscle. Furthermore, this insulin degrading enzyme was found to have no effect on the structure of the insulin receptor nor to be linked to the insulin receptor either on the plasma membrane of cells or when they are shed into the media. The present studies suggest that the IM-9 lymphocytes, which have been extensively used to study the human insulin receptor, may also be a good system for studying human insulin degrading enzymes.