Ouimet H, Freedman J E, Loscalzo J
Cardiovascular Division, Brigham and Women's Hospital, Boston, Massachusetts.
Biochemistry. 1994 Mar 15;33(10):2970-6. doi: 10.1021/bi00176a029.
Plasminogen and tissue-type plasminogen activator bind to the platelet surface, and as a result, the catalytic efficiency of plasminogen activation is significantly enhanced. The plasmin that is generated on or near the platelet is known to affect a number of platelet surface events. For this reason, we examined the effect of plasmin on platelet-surface plasminogen activation and its determinants. Specifically, we measured the effects of plasmin treatment of platelets (1 caseinolytic unit/mL for 1 h at 37 degrees C) on plasminogen, tissue-type plasminogen activator, and plasmin binding to the unactivated and ADP-activated platelet surface; and on the kinetics of plasminogen activation on the platelet surface. Following plasmin treatment, the number of plasminogen binding sites on unactivated platelets increased by 78% (from 46,000 +/- 4000 to 88,000 +/- 9000 sites/platelet), while the number of tissue-type plasminogen activator sites did not change, and the number of diisopropyl fluorophosphate (DFP)-inactivated plasmin (DFP-plasmin) binding sites decreased by 31% (from 92,000 +/- 11,000 to 65,000 +/- 7000 sites/platelet); the dissociation constants (Kds) for each of these binding processes did not change significantly following treatment. On ADP-activated platelets, plasmin treatment increased the number of plasminogen binding sites by 41% (from 188,000 +/- 17,000 to 265,000 +/- 25,000 sites/platelet), decreased the number of plasmin binding sites by 28% (from 219,000 +/- 41,000 to 157,000 +/- 24,000 sites/platelet), and did not affect the number of tissue-type plasminogen activator sites; again, the Kds for each of these binding processes did not change significantly following treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
纤溶酶原和组织型纤溶酶原激活剂与血小板表面结合，因此，纤溶酶原激活的催化效率显著提高。已知在血小板上或其附近产生的纤溶酶会影响许多血小板表面事件。因此，我们研究了纤溶酶对血小板表面纤溶酶原激活及其决定因素的影响。具体而言，我们测量了用纤溶酶处理血小板（在37℃下以1酪蛋白溶解单位/毫升处理1小时）对纤溶酶原、组织型纤溶酶原激活剂以及纤溶酶与未激活和ADP激活的血小板表面结合的影响；以及对血小板表面纤溶酶原激活动力学的影响。纤溶酶处理后，未激活血小板上纤溶酶原结合位点的数量增加了78%（从46,000±4000个位点/血小板增加到88,000±9000个位点/血小板），而组织型纤溶酶原激活剂位点的数量没有变化，二异丙基氟磷酸酯（DFP）灭活的纤溶酶（DFP-纤溶酶）结合位点的数量减少了31%（从92,000±11,000个位点/血小板减少到65,000±7000个位点/血小板）；处理后这些结合过程的解离常数（Kds）没有显著变化。在ADP激活的血小板上，纤溶酶处理使纤溶酶原结合位点的数量增加了41%（从188,000±17,000个位点/血小板增加到265,000±25,000个位点/血小板），使纤溶酶结合位点的数量减少了28%（从219,000±41,000个位点/血小板减少到157,000±24,000个位点/血小板），并且不影响组织型纤溶酶原激活剂位点的数量；同样，处理后这些结合过程的Kds没有显著变化。（摘要截短于250字）
