Greenberg C S, Miraglia C C, Rickles F R, Shuman M A
J Clin Invest. 1985 May;75(5):1463-70. doi: 10.1172/JCI111849.
Thrombin cleavage of blood coagulation Factor XIII (a2b2) and fibrinogen was studied during in vitro clotting to determine the physiologic sequence of these events. First, the time course of fibrin formation and cleavage of Factor XIII was measured in platelet-rich plasma. Cleavage of fibrinogen was measured by using a radioimmunoassay for fibrinopeptide A. Conversion of trace amounts of radioiodinated a-chains of 125I-Factor XIII to thrombin-modified a-chains was measured in unreduced 10% sodium dodecyl sulfate-polyacrylamide gels. During spontaneous clotting, a similar percentage of 125I-Factor XIII and fibrinogen was cleaved at each time point. Visible gelation of polymerized fibrin monomer occurred when 24 +/- 8% of fibrinogen was cleaved and 21 +/- 6% of Factor XIII was converted to Factor XIII'. Thrombin cleavage of Factor XIII and fibrinogen was also studied in platelet-poor plasma to which thrombin was added. In order to measure Factor XIIIa activity, fibrin polymerization was completely inhibited by the addition of Gly-Pro-Arg-Pro. Factor XIIIa formation was measured by the incorporation of [3H]putrescine into casein. The concentration of added thrombin required to cleave 50% of fibrinogen and Factor XIII was 0.65 U/ml and 0.35 U/ml, respectively. The rate of cleavage of fibrinogen by thrombin was 43-fold greater than cleavage of Factor XIII. Lower Gly-Pro-Arg-Pro concentrations were used to determine the effects of incompletely inhibiting fibrin polymerization on cleavage of Factor XIII and fibrinogen. Thrombin cleavage of Factor XIII but not fibrinogen was dependent on the extent of fibrin polymerization. The more marked the degree of inhibition of fibrin polymerization, the slower the rate of Factor XIIIa formation. Thus, in platelet-rich plasma, thrombin cleavage of Factor XIII and fibrinogen are closely related events during spontaneous clotting. Furthermore, cleavage of Factor XIII during clotting is enhanced by fibrin polymerization in platelet-poor plasma.
在体外凝血过程中研究了凝血因子 XIII（a2b2）和纤维蛋白原的凝血酶裂解情况，以确定这些事件的生理顺序。首先，在富含血小板的血浆中测量纤维蛋白形成和因子 XIII 裂解的时间进程。通过使用针对纤维蛋白肽 A 的放射免疫测定法测量纤维蛋白原的裂解。在未还原的 10%十二烷基硫酸钠 - 聚丙烯酰胺凝胶中测量痕量放射性碘化的 125I - 因子 XIII 的α链向凝血酶修饰的α链的转化。在自发凝血过程中，在每个时间点，125I - 因子 XIII 和纤维蛋白原被裂解的百分比相似。当 24±8%的纤维蛋白原被裂解且 21±6%的因子 XIII 转化为因子 XIII'时，聚合的纤维蛋白单体出现可见凝胶化。还在添加了凝血酶的贫血小板血浆中研究了凝血酶对因子 XIII 和纤维蛋白原的裂解。为了测量因子 XIIIa 活性，通过添加甘氨酰 - 脯氨酰 - 精氨酰 - 脯氨酸完全抑制纤维蛋白聚合。通过将[3H]腐胺掺入酪蛋白中来测量因子 XIIIa 的形成。裂解 50%的纤维蛋白原和因子 XIII 所需的添加凝血酶浓度分别为 0.65 U/ml 和 0.35 U/ml。凝血酶对纤维蛋白原的裂解速率比对因子 XIII 的裂解速率大 43 倍。使用较低浓度的甘氨酰 - 脯氨酰 - 精氨酰 - 脯氨酸来确定不完全抑制纤维蛋白聚合对因子 XIII 和纤维蛋白原裂解的影响。凝血酶对因子 XIII 的裂解而非对纤维蛋白原的裂解取决于纤维蛋白聚合的程度。纤维蛋白聚合的抑制程度越明显，因子 XIIIa 的形成速率越慢。因此，在富含血小板的血浆中，在自发凝血过程中凝血酶对因子 XIII 和纤维蛋白原的裂解是密切相关的事件。此外，在贫血小板血浆中，凝血过程中因子 XIII 的裂解因纤维蛋白聚合而增强。
