Identification of renal cathepsin B as a human prorenin-processing enzyme.

摘要: Prorenin, the inactive biosynthetic precursor of renin, is proteolytically cleaved in renal juxtaglomerular cells to renin. The activity renin rate-limiting for generation angiotensin II circulation. We identified a thiol protease which activates and accurately cleaves 43-amino acid prosegment human recombinant prorenin. In current studies, 6.5 mg this was purified from cortex using three-step procedure dependent upon Leu-Leu-arginyl affinity chromatography. This represented an overall 766-fold purification resulted three protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis molecular weights 30,000, 25,000, 24,000. All cross-reacted with anti-human liver cathepsin B antibody immunoblot analysis; electrolution each band amino-terminal sequence analysis confirmed that Mr 30,000 mature 25,000 24,000 were subunits. pH optimum hydrolysis pure prorenin by 6, Michaelis-Menten constant, Km, reaction 1.4 x 10(-9) M. Immunostaining kidney sheep demonstrated presence areas kidney, as well proximal tubules. Electron microscopic immunohistochemistry same dense secretory granules cells. Renin also shown be present these granules. study provides both biochemical morphological evidence prorenin-processing enzyme.