The association of metalloendopeptidase EC 3.4.24.15 at the extracellular surface of the AtT-20 cell plasma membrane

Abstract

Endopeptidase EC 3.4.24.15 (EP24.15) is a soluble, neuropeptide- degrading metalloenzyme, widely expressed in the brain, pituitary and gonads. For the physiological metabolism of neuropeptides, the enzyme should be located extracellularly, either associated with the plasma membrane or in the extracellular milieu. Western immunoblot analyses of crude cytosolic and post-nuclear membrane fractions prepared by differential centrifugation revealed a slightly smaller molecular mass (~ 2 kDa) for EP24.15 in the post-nuclear membrane fraction. This smaller EP24.15 species was also present in an enriched fraction of plasma membrane prepared by Percoll gradient centrifugation. To ascertain whether EP2..