In vitro degradation of angiotensin II (A-II) by human placental subcellular fractions, pregnancy sera and purified placental aminopeptidases.
The degradation of angiotensin II (Asp1-Arg2-Val3-Tyr4-Ile5-His6-Pro7-Phe8: A-II) by human placental particulate and soluble fractions, pregnant and non-pregnant sera, and highly purified placental enzymes such as placental leucine aminopeptidase P-LAP (microsomal), retroplacental serum P-LAP (soluble), aminopeptidase A and post-proline endopeptidase, was studied by measuring liberated amino acids by high performance liquid chromatography. Placental particulate and soluble fractions degraded A-II almost completely into single amino acids. The purified P-LAP (microsomal) actively liberated five amino acids from the N-terminal. The placental particulate fraction containing P-LAP (microsomal) also actively liberated these amino acids. The purified aminopeptidase A liberated Asp1 very actively as expected. When the ratio of the velocity of liberation of each amino acid to P-LAP activity measured with leu-p-nitroanilide as a substrate was calculated, placental soluble fraction liberated Asp1 very actively, but the liberation rate of Asp1 with the purified P-LAP (soluble) was very low. Therefore it seems that the enzyme in the placental soluble fraction and pregnancy serum responsible for the Asp1 liberation is not P-LAP (soluble), but aminopeptidase A. The mixture of purified P-LAP (soluble) and aminopeptidase A showed higher liberation rate of Arg2 and Val3 than that with purified aminopeptidase A alone, demonstrating that once the N-terminal Asp1 was liberated, the P-LAP (soluble) attacks the shorter peptide (angiotension III) very actively. It was concluded that P-LAP (microsomal) together with aminopeptidase A seem to contribute greatly to the degradation of A-II in pregnant women.
D000596:Amino Acids / Q000378:metabolism; D000626:Aminopeptidases / Q000378:metabolism*; D000804:Angiotensin II / Q000031:analogs & derivatives* / Q000378:metabolism*; D010450:Endopeptidases / Q000378:metabolism; D005260:Female; D043384:Glutamyl Aminopeptidase; D006801:Humans; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D000085822:Prolyl Oligopeptidases; D012697:Serine Endopeptidases; D013347:Subcellular Fractions / Q000378:metabolism*
D000596:Amino Acids; D000804:Angiotensin II; D010450:Endopeptidases; D000626:Aminopeptidases; D007931:Leucyl Aminopeptidase; D043384:Glutamyl Aminopeptidase; D012697:Serine Endopeptidases; C000705287:PREPL protein, human; D000085822:Prolyl Oligopeptidases