López Bernal A, Newman G E, Phizackerley P J, Bryant-Greenwood G, Keeling J W
Nuffield Department of Obstetrics and Gynaecology, University of Oxford, John Radcliffe Hospital, Headington, U.K.
Eur J Obstet Gynecol Reprod Biol. 1992 Feb 28;43(3):185-92. doi: 10.1016/0028-2243(92)90172-u.
Phospholipase A2 activity (EC 3.1.1.4) was estimated in low-speed supernatants of human placenta by measuring the release of arachidonic acid from phosphatidylcholine, 1-stearoyl-2-[3H]arachidonyl and other phospholipids under alkaline conditions (pH 8). Activity was calcium dependent and followed Michaelis-Menten kinetics with an apparent Km of 0.19 (SD 0.04) mM and a Vmax of 486 (SD 52) pmol/mg protein per h. Placental phospholipase A2 activity was relatively high in early pregnancy (8-11 weeks gestation) and following spontaneous preterm labour (31-34 weeks), but decreased significantly towards term with no changes in relation to parturition. By contrast, activity in the fetal membranes (amnion and chorio-decidua) was low after preterm labour and increased significantly towards term. The placenta and fetal membranes have the capacity to contribute to the increased intra-uterine release of arachidonic acid and eicosanoids that occurs during term and preterm labour, but at present there is no evidence that this increase involves direct changes in phospholipase A2 activity.
通过在碱性条件（pH 8）下测量花生四烯酸从磷脂酰胆碱、1-硬脂酰-2-[3H]花生四烯酰及其他磷脂中的释放量，来估算人胎盘低速上清液中的磷脂酶A2活性（EC 3.1.1.4）。该活性依赖于钙，遵循米氏动力学，表观Km为0.19（标准差0.04）mM，Vmax为486（标准差52）pmol/mg蛋白质每小时。胎盘磷脂酶A2活性在妊娠早期（妊娠8 - 11周）及自然早产（31 - 34周）时相对较高，但在足月时显著下降，与分娩无关。相比之下，胎膜（羊膜和绒毛膜 - 蜕膜）的活性在早产时较低，在足月时显著增加。胎盘和胎膜有能力促进足月和早产期间子宫内花生四烯酸和类花生酸释放的增加，但目前没有证据表明这种增加涉及磷脂酶A2活性的直接变化。
