MULTIPLE FORMS OF HUMAN RENIN - PURIFICATION AND CHARACTERIZATION

Human renin (EC 3.4.99.19) was purified from a juxtaglomerular cell tumor with a high renin content, 24.2 Goldblatt units/mg of protein. The purification procedure comprised 3 steps: gel filtration, DEAE-cellulose chromatography and preparative isoelectric focusing. Forms of renin (5) amounting to 5.3 mg of enzyme were obtained with isoelectric points of 4.95, 5.10, 5.35, 5.55 and 5.70. They were all glycoproteins. The 3 major fractions had very similar specific activities, 868, 860 and 809 Goldblatt units/mg of protein. The fractions produced a single band on analytical isoelectric focusing and a single arc on immunoelectrophoresis. On polyacrylamide gel electrophoresis at pH 7.8, each fraction consisted of 2 renin bands with the same MW, but different net charges. The MW determined by gel filtration and Fergusson plot analysis on polyacrylamide gel was 38,000-42,000. The optimum pH determined on N-acetyltetradecapeptide substrate was 6.5, and the Km was 6.8 .times. 10-6 M. These parameters were identical with those for standard human kidney renin. Antibodies raised against tumor renin completely inhibited the activity of both tumor and standard renin. Under dissociating conditions, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel electrophoresis in the presence of 6 M urea, part of the purified enzyme dissociated into 2 smaller fragments (MW = 20,000 and 25,000) containing renin activity.