Renin was purified from 47 kg of hog kidney to produce enough enzyme for enzymatic and physicochemical characterization. The procedure included extraction at pH 3.5 in the presence of protease inhibitors, two ammonium sulfate precipitations, ion exchange chromatography on Sepharose-hexamethylenediamino-pepstatin gel, gel filtration, and isoelectric focusing. Renin, 2.3 mg, with a specific activ...