Geng D, Chura J, Roberts M F
Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02167, USA.
J Biol Chem. 1998 May 15;273(20):12195-202. doi: 10.1074/jbc.273.20.12195.
The activity of bacterial phospholipase D (PLD), a Ca2+-dependent enzyme, toward phosphatidylcholine bilayers was enhanced 7-fold by incorporation of 10 mol % phosphatidic acid (PA) in the vesicle bilayer. Addition of other negatively charged lipids such as phosphatidylinositol, phosphatidylmethanol, and oleic acid either inhibited or had no effect on enzyme activity. Only negatively charged lipids with a free phosphate group, phosphatidylinositol 4-phosphate and lyso-PA, had the same effect as PA on enzyme activity. Changes in vesicle curvature and fusion were not the reason for PA activation; rather, a metal ion-induced lateral segregation of PA in the vesicle bilayer correlated with PLD activation. Significant PA activation was also observed with monomer phosphatidylcholine substrate upon the addition of PA vesicles. The PA activation was caused by Ca2+.PA interacting with PLD at an allosteric site other than active site.
细菌磷脂酶D（PLD）是一种依赖Ca2+的酶，当在囊泡双层中掺入10摩尔%的磷脂酸（PA）时，其对磷脂酰胆碱双层的活性提高了7倍。添加其他带负电荷的脂质，如磷脂酰肌醇、磷脂酰甲醇和油酸，要么抑制酶活性，要么对酶活性没有影响。只有带有游离磷酸基团的带负电荷脂质，即磷脂酰肌醇4-磷酸和溶血磷脂酸，对酶活性具有与PA相同的作用。囊泡曲率和融合的变化不是PA激活的原因；相反，金属离子诱导的PA在囊泡双层中的横向分离与PLD激活相关。在添加PA囊泡后，对于单体磷脂酰胆碱底物也观察到了显著的PA激活。PA激活是由Ca2+.PA在活性位点以外的变构位点与PLD相互作用引起的。
