title: Human placental oxytocinase and its relationship to pregnancy plasma oxytocinase.
abstract: Plasma "oxytocinase of pregnancy" and three placental "oxytocinase" fractions from human placental extracts were compared. On  the basis of acrylamide-agarose chromatography, polyacrylamide gel electrophoresis, substrate specificity, heat liability and relative insensitiveness to L-methionine, it is concluded that placental enzyme activities, present in the second acrylamide-agarose peak, are identical with the plasma "pregnancy oxytocinase" and are to be regarded as its source. The hypothesis of a transplacental passage of placental peak II oxytocinase in the blood compartment of the mother seems well supported. Heat treatment of the placental extracts uncovered a minor activity behaving like Oya's microsomal oxytocinase, which is totally unlike the plasma oxytocinase and plays no part in the increased oxytocinase activity of human pregnancy plasma. A hitherto undescribed enzyme activity shares with the pregnancy oxytocinase its specificity towards L-leucyl-beta-naphthylamide and di-S-S-L-cysteinyl-beta-naphthylamide, its heat lability and realtive insensitiveness to L-methionine. However, this activity is carried by a protein of much lower molecular weight as judged by acrylamide-agarose chromatography, which shows only a single activity band on polyacrylamide gel electrophoresis.
mesh_terms: D000135:Acid Phosphatase / Q000032:analysis; D000626:Aminopeptidases / Q000032:analysis*; D002847:Chromatography, Agarose; D010122:Cystinyl Aminopeptidase / Q000032:analysis* / Q000097:blood; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008247:Lysosomes / Q000201:enzymology; D008715:Methionine / Q000494:pharmacology; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D013379:Substrate Specificity
chemical_list: D008715:Methionine; D000135:Acid Phosphatase; D000626:Aminopeptidases; D010122:Cystinyl Aminopeptidase