Koistinen R, Huhtala M L, Stenman U H, Seppälä M
Clin Chim Acta. 1987 May 15;164(3):293-303. doi: 10.1016/0009-8981(87)90304-4.
Human amniotic fluid was found to contain a protein which is immunochemically indistinguishable from placental protein PP12. This protein was purified by gel filtration, hydrophobic interaction high performance liquid chromatography and anion-exchange chromatography. The relative molecular mass as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis was 34,000, and the isoelectric point was 4.9. Tryptic peptides of amniotic fluid PP12 as determined by reversed phase high performance liquid chromatography were similar to those of placental PP12. Both had the N-terminal amino acid sequence Ala-Pro-Trp-Gln-, which is the same as previously reported for a somatomedin-binding protein. Both placental PP12 and amniotic fluid PP12 were found to bind somatomedin C (IGF-I) with high affinity, Ka = 1 X 10(9) l/mol). Amniotic fluid is an ideal source of this somatomedin-binding protein, and the purification method described allows rapid isolation of PP12 under mild conditions which are essential for studies on its biological function.
人们发现，人羊水含有一种蛋白质，该蛋白质在免疫化学上与胎盘蛋白PP12无法区分。通过凝胶过滤、疏水作用高效液相色谱法和阴离子交换色谱法对该蛋白质进行了纯化。经十二烷基硫酸钠聚丙烯酰胺凝胶电泳测定，其相对分子质量为34,000，等电点为4.9。通过反相高效液相色谱法测定，羊水PP12的胰蛋白酶肽与胎盘PP12的胰蛋白酶肽相似。两者都具有N端氨基酸序列Ala-Pro-Trp-Gln-，这与先前报道的一种生长调节素结合蛋白的序列相同。研究发现，胎盘PP12和羊水PP12均能以高亲和力（Ka = 1×10⁹ l/mol）结合生长调节素C（胰岛素样生长因子-I）。羊水是这种生长调节素结合蛋白的理想来源，所述纯化方法能够在温和条件下快速分离PP12，这对于研究其生物学功能至关重要。
