Characteristics of an Enzyme That Inactivates Angiotensin II (Angiotensinase C).
OKLAHOMA UNIV MEDICAL CENTER OKLAHOMA CITY
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Angiotensinase C was partially purified from swine kidney cortex, where it occurs in a lysosomal fraction. The enzyme was also present in human urine, leucocytes and platelets, but absent from red blood cells or plasma. Angiotensinase C breaks bonds of proline at an acid pH provided the imino group of proline is protected and it is in the penultimate position. The C-terminal amino acid liberated from the proline link has to have a free carboxyl group. The substrates include angiotensin II and other peptides. A sensitive fluorometric assay technique was developed based on measuring the amount of DNS-Pro released by the enzyme from the dansylating prolylphenyl-alanine DNS-Pro-Phe substrate. The inhibition pattern and substrate specificity indicated that the enzyme is not identical with cathepsins, carboxypeptidases, kininases or other angiotensinases. Author