[Post-translational proteolytic maturation of prosomatostatin. Cellular and molecular approach]

Somatostatins -14 and -28 are generated from a single (mammals) or two distinct (teleostean fishes) biosynthetic precursors by selective cleavage at either a dibasic (Arg-Lys) or a monobasic (Arg) site. This prohormone obviously constitutes an excellent model to study post-translational proteolytic events both at the cellular and molecular levels. Using a combination of techniques including subcellular fractionation, intracellular transport blockage and electron microscopy immunocytochemical observations, we have demonstrated unequivocally that both monobasic and dibasic proteolytic maturation occur in the Golgi apparatus of either rat brain cortex or hypothalamic cells or for somatostatin producing cells of Lophius piscatorius Brockmann organs. An arginine selective endoprotease, putative converting enzyme of prosomatostatin into somatostatin -28, has been purified and characterized from the rat intestinal mucosa.