title: Purification and characterization of human placental microsomal aminopeptidase: immunological difference between placental microsomal aminopeptidase and pregnancy serum cystyl-aminopeptidase.
abstract: Human placental microsomal aminopeptidase (microsomal PAP) was purified 3,880-fold from human placenta and characterized. The enzyme was solubilized from membrane fractions with Triton X-100 and also trypsin digestion, and subjected to zinc sulfate fractionation, chromatographies with DE-52, hydroxylapatite, Sephacryl S-300 and lentil lectin-Sepharose 4B, and finally affinity chromatography with bestatin-Sepharose 4B. Microsomal PAP was separated from aminopeptidase A (AAP) by affinity chromatography. The apparent relative molecular mass (Mr) of the enzyme was estimated to be 220,000 by high-performance liquid chromatography with an aqueous gel column. The purified enzyme gave almost a single band with a molecular mass of 140,000 by sodium dodecyl sulfate (SDS) gel electrophoresis. The isoelectric point of the enzyme was 5.2. The purified enzyme was most active at pH 8.0 with L-leucine-p-nitroanilide as substrate; the Km value for this substrate was 1.1 mmol/l. The microsomal PAP was immunologically different from the pregnancy serum cystyl aminopeptidase (serum PAP).
mesh_terms: D000626:Aminopeptidases / Q000037:antagonists & inhibitors / Q000302:isolation & purification* / Q000378:metabolism; D001667:Binding, Competitive; D018826:CD13 Antigens; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D010122:Cystinyl Aminopeptidase / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D007525:Isoelectric Focusing; D007700:Kinetics; D008970:Molecular Weight; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011863:Radioimmunoassay; D013379:Substrate Specificity
chemical_list: D000626:Aminopeptidases; D018826:CD13 Antigens; D010122:Cystinyl Aminopeptidase