稀土及其配合物对蛇毒磷脂酶A_2活性的影响

分别研究了三价稀土离子 (La3 + ,Eu3 + ,Dy3 + ,Yb3 + )、二乙三胺五乙酸及其衍生物二乙三胺五乙酸 -双二甲酰胺 ,二乙三胺五乙酸 -双 (异烟肼 )与稀土离子的配合物以及Tb -谷氨酰胺配合物对蛇毒磷脂酶A2 活性的影响 .浓度低于 <3μmol/L的稀土离子可以激活磷脂酶A2 ,浓度大于 5 μmol/L后稀土离子对酶活性表现出抑制作用 ;外源Ca2 + 离子的加入可以缓解稀土离子对酶活性的抑制作用 ,表明稀土离子和钙离子是竞争性地结合在酶的活性部位 ;稀土离子和二乙三胺五乙酸及其衍生物的配合物对酶活性没有明显影响 ;Tb -谷氨酰胺在浓度大于 10 μmol/L后开始抑制酶的活性

Effects of Rare Earth Ions and Their Complexes on the Activity of Snake Venom Phospholipase A2

Effects have been investigated of trivalent rare earth ions (La 3+ , Eu 3+ , Dy 3+ , Yb 3+ ) and their complexes with diethylenetriamine pentaacetic acid (DTPA) or DTPA's derivatives bisdimethylamide- diethylenetriamine pentaacetic acid (DTPA-BDMA), bisisonicotinyl-diethylenetriamine pentaacetic acid (DTPA-BIN) on the activity of phospholipase A 2 (PLA 2) obtained from Chinese Agkistrodon blomhoffii Ussurensis venom. The results revealed that rare earth ions could stimulate PLA 2's activity at a concentration of below 3μmol/L, while the activity of PLA 2 is inhibited when the concentration is higher than 5μmol/L. Exogenous calcium ion could decrease the inhibitory effects of rare ions, indicating that rare ions competitively substitute for calcium ion located in the active site of PLA 2. Rare earth complexes with DTPA or its derivatives produced significant effects on PLA 2's activity. When the concentration is below 10 μmol/L, Tb-glutamine complex could also stimulate PLA 2's activity, leaving a strong inhibitory effects on the activity of PLA 2 when its concentration is higher than 10 μmol/L, mostly due to the fact that the disassociation constant of Tb-glutamine is much less than that of lanthanide ions with DTPA.