PMID: 6401723Jan 25, 1983Paper

A high molecular weight metalloendoprotease from the cytosol of mammalian cells.

The Journal of Biological Chemistry
R J Kirschner, A L Goldberg

Abstract

In red cell lysates, three soluble proteases hydrolyze insulin at pH 8.5. One of these enzymes was purified to homogeneity by conventional chromatographic techniques. It appears to be a metalloprotease since it is inhibited by EDTA, o-phenanthroline, and 8-hydroxyquinoline, the metal-depleted enzyme can be reactivated by micromolar levels of Zn2+, Co2+, or Mn2+, and it is not inhibited by reagents specific for carboxyl, serine or thiol proteases. This enzyme has an apparent molecular weight of 300,000 +/- 25,000, and electrophoresis in sodium dodecyl sulfate indicates a single band with an Mr = 115,000 +/- 10,000. End group analysis and automated Edman degradation of the products of proteolysis showed that it is an endoprotease which cleaves on the NH2-terminal side of large hydrophobic amino acids. Although various small polypeptides with Mr = 2300-3500 are hydrolyzed (e.g. insulin chains, glucagon, and calcitonin), a variety of larger proteins are not degraded (e.g. casein and globin). The latter proteins, however, are converted to substrates for the metalloprotease by digestion with the ATP-stimulated endoprotease from erythrocytes. Thus, the metalloprotease may play a role in the ATP-dependent pathway for degrading proteins...Continue Reading

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