PHYSICOCHEMICAL CHARACTERISTICS OF THE ANGIOTENSIN-CONVERTING ENZYME FROM BOVINE LUNGS

The angiotensin-converting enzyme from bovine lungs was isolated by chromatographic methods with a yield of 25-30%, degree of purification 2200-2600-fold. The concentration of active molecules in the enzyme preparations was 70-100% according to the results of titration with the inhibitor SQ 20,881. The molecular weight of the enzyme according to electrophoresis was approximately 132 kD; the maximum radium of the molecules, according to the results of electron microscopy, was 68 +/- 9 angstrom. Five isoforms of the enzyme were detected, to which the following values of pI correspond: 4.85, 4.7, 4.54, 4.38, 4.3. The kinetic parameters of the hydrolysis of three synthetic peptide substrates and the constants of activation of hydrolysis of the substrate Z-Phe-His-Leu by chloride anions were determined.