Effects of Low Molecular Weight Peptides and Divalent Cations on Degradation and Binding of Angiotensin II

Authors:
  • SMS. Mizutani
    S. Mizutani
  • OKO. Kurauchi
    O. Kurauchi
  • MKM. Kasugai
    M. Kasugai
  • ONO. Narita
    O. Narita
  • YTY. Tomoda
    Y. Tomoda
Publisher website
Google Scholar
Abstract
The effects of peptide inhibitors (bestatin and amastatin) and divalent cations (Ca2+ and Co2+) on the velocity of Asp1 liberation from angiotensin II (A-II) by human placental membrane fractions and binding of 125I A-II to human placental membranes were tested at 22 °C and 4 °C. Asp1 liberation was measured by high performance liquid chromatography. As expected, the degradation and binding of A-II were temperature sensitive, with both being at 4 °C than at 22 °C. While amastatin (10-4M) and bestatin 10-6M) significantly reduced the velocity of Asp1 liberation from A-II to about 45%, amastatin (10-4M) and bestatin (10-4M) increased 125I A-II binding to 125% and 130%, respectively. Ca2+ (10 mM)and Co2+ (10 mM) activated the velocity of Asp1 liberation from A-II to 140% and 120%, respectively at 22 °C. Ca2+ (10-1 M) and Co2+ (10 mM) also enhanced 125I A-II binding about 130%. Previously we showed that the A-II degrading activity found in human placental membrane fractions is mainly due to aminopeptidases A and M. Since amastatin and bestatin are the specific inhibitors for aminopeptidases A and M, and since Ca2+ and Co2+ are the activators for aminopeptidase A and aminopeptidase M, respectively, it is conceivable that the enzymes regulate the levels of A-II and, therefore, that they may play an important role in the binding of A-II to human placental membrane fractions.

This publication has 20 references indexed in Scilit: