Abstract:

The stimulatory effect of lysophosphatidylcholine (lyso-PC) on ATP and ρ-nitrophenyl phosphate (PNPP) hydrolysis by the plasma membrane H+-ATPase from soybean (Glycine max (L.) Merr.) hypocotyls was studied. Results showed that lyso-PC stimulated the hydrolysis of ATP; ATP hydrolysis was enhanced dramatically when lyso-PC was within 0-0.03%, and increased slightly when lyso-PC was higher than 0.03%. At the concentration of 0.03%, lyso-PC stimulated ATP hydrolysis by 80.5%. Kinetics analysis showed that V max increased from 0.46μmol Pi·mg-1 protein·min-1 to 0.87 μmol Pi·mg-1 protein·min-1 while Km increased from 0.88 mmol/L to 1.15 mmol/L under lyso-PC treatment. The optimum pH of ATP hydrolysis was shifted from 6.5 to 7.0. Moreover, it was found lyso-PC enhanced the inhibition of ATP hydrolysis by hydroxylamine. In the presence of 200 mmol/L hydroxylamine, ATP hydrolysis was inhibited by 74.4%, while it was inhibited by 84.4% when treated with lyso-PC. However, PNPP hydrolysis and the inhibitory effect of vanadate were not affected by lyso-PC. The above results indicated that the kinase domain might be an action site or regulatory region of the C-terminal autoinhibitory domain in the plant plasma membrane H+-ATPase.

溶血卵磷脂对大豆下胚轴质膜H+-ATPase ATP 和对-硝基苯磷酸水解活性的影响
邱全胜*  张楠
（北京师范大学生命科学学院，北京100875）

Key words: lysophosphatidylcholine (lyso-PC), soybean hypocotyls, plasma membrane H+-ATPase, C-terminal autoinhibitory domain, kinase domain