Biagini G, Salvolini E, Pugnaloni A, Rabini R A, Cester N, Romanini C, Staffolani R, Mazzanti L
Instituti di Morfologia Umana Normale e Biochimica, Universita' di Roma, Tor Vergata, Italy.
Mol Cell Biochem. 1995 Oct 4;151(1):15-20. doi: 10.1007/BF01076890.
A decrease of Na+/K(+)-ATPase activity has been reported in syncytiotrophoblast plasma membrane (SPM) obtained from pregnancy induced hypertensive (PIH) women. The aim of the present work was to verify if the reported modifications in activity are due to a decreased number of enzymatic molecules or to a conformational change of the enzyme itself. Morphological studies were performed in order to better understand the relations between the enzymatic protein and the lipid bilayer. Kinetic studies were also performed. SPM obtained from PIH showed: i) an increased affinity of Na+/K(+)-ATPase for ouabain binding, ii) a significant change in the maximum velocity of the enzyme, iii) a higher distribution factor (DF) of intramembrane particles (IMPs) in the exoplasmic face of the membrane, iv) a decreased mean diameter of IMPs both in the protoplasmic and exoplasmic faces, v) a decreased number of IMPs in the exoplasmic face. In conclusion, a conformational modification seems to be at the basis of the decreased Na+/K(+)-ATPase activity during PIH as suggested by binding, ultrastructural and kinetic data herein reported.
据报道，妊娠高血压（PIH）女性的合体滋养层细胞膜（SPM）中钠钾ATP酶（Na+/K(+)-ATPase）活性降低。本研究的目的是验证所报道的活性改变是由于酶分子数量减少还是酶本身的构象变化所致。进行了形态学研究，以便更好地理解酶蛋白与脂质双层之间的关系。还进行了动力学研究。从PIH患者获得的SPM显示：i）钠钾ATP酶对哇巴因结合的亲和力增加；ii）酶的最大速度发生显著变化；iii）膜外质面内膜内颗粒（IMP）的分布因子（DF）更高；iv）原生质面和膜外质面IMP的平均直径减小；v）膜外质面IMP数量减少。总之，如本文报道的结合、超微结构和动力学数据所示，构象修饰似乎是PIH期间钠钾ATP酶活性降低的基础。
