Purification and partial characterization of human angiotensinogen.

Renin substrate was initially extracted from human plasma by (NH4)2SO4 followed by chromatography on Sephadex G-150, DEAE cellulose, calcium phosphate gel, isoelectric focusing and preparative polyacrylamide gel electrophoresis. On the basis of one mol of angiotensin per mol of substrate, the purity of the preparation is in excess of 95%. On analytical polyacrylamide gel electrophoresis in the presence of 1% sodium dodecyl sulfate or 8 M urea, the protein appears homogenous. In addition, the purified protein shows only one preciptin line against anti-normal human serum on either Ouchterlony immunodiffision or immunoelectrophoresis. The biological activity appears similar to "native" renin substrate since the Km is the same as that reported for the renin reaction in whole plasma. The molecular weight was determined as 110 000 by gel filtration and polyacrylamide gel electrophoresis; amino acid analysis of the human substrate differs from that reported for hog, especially in the Asp, Glu and Gly composition.