Iioka H, Akada S, Sakamoto Y, Shimamoto T, Yamada Y, Moriyama I S, Ichijo M
Department of Obstetrics and Gynecology Nara Medical University, Japan.
Placenta. 1993 May-Jun;14(3):333-9. doi: 10.1016/s0143-4004(05)80431-x.
The enzymatic properties of ADP (adenosine diphosphate) degradation in human placental syncytiotrophoblast brush border membrane vesicles (BBMV) were explored and the following results were obtained. BBMV had high ADP degrading activity compared to homogenate of placental villi. ADP degrading activity of BBMV; 1.05 +/- 0.05 mumol/mg protein/min placental villi was 21 times higher than that of homogenate of placental villi. Hydrolysis of ADP by BBMV follows Michaelis-Menten saturation kinetics with an apparent Km of 10.9 +/- 0.8 microM and Vmax of 2.10 +/- 0.17 mumol/mg protein/min. The enzyme has a divalent cation requirement. EDTA (2 mM) was found to abolish ADP degrading activity but this could be restored by the addition of either magnesium or calcium ions. Maximum enzyme activity of ADP degradation in BBMV was observed at a pH close to 8.0. The enzyme was insensitive to vanadate, levamisole, oligomycin, ouabain and N-ethylmaleimide (NEM), omeprazole and adenosine (5') pentaphospho (5') adenosine.
对人胎盘合体滋养层刷状缘膜囊泡（BBMV）中ADP（二磷酸腺苷）降解的酶学特性进行了研究，结果如下。与胎盘绒毛匀浆相比，BBMV具有较高的ADP降解活性。BBMV的ADP降解活性为1.05±0.05 μmol/mg蛋白/分钟，胎盘绒毛的ADP降解活性是胎盘绒毛匀浆的21倍。BBMV对ADP的水解遵循米氏饱和动力学，表观Km为10.9±0.8 μM，Vmax为2.10±0.17 μmol/mg蛋白/分钟。该酶需要二价阳离子。发现EDTA（2 mM）可消除ADP降解活性，但通过添加镁离子或钙离子可恢复该活性。在接近pH 8.0时观察到BBMV中ADP降解的最大酶活性。该酶对钒酸盐、左旋咪唑、寡霉素、哇巴因、N-乙基马来酰亚胺（NEM）、奥美拉唑和腺苷（5'）五磷酸（5'）腺苷不敏感。
