Fenton J W, Wideman C S, Evatt B L
Clin Chem. 1986 Feb;32(2):320-4.
Thrombin-induced clotting times were inversely proportional to fibrinogen concentrations within the range of 98 to 2900 nmol/L; these reciprocal velocity measurements had units of seconds per clot. By analogy with classical enzyme kinetics, we defined rectangular hyperbolic parameters where Km(clot) ranged from 0.14 to 0.56 mumol/L and kclot from 0.020 to 0.075 clot per second. Specificity ratios (kclot/Km(clot)) showed that reconstituted lyophilized human plasma is as good, if not better, a source of clottable fibrinogen as the purified protein itself. These ratios also showed that the presence of greater than 98% of the autoproteolytic forms (beta- and gamma-thrombins) of the human enzyme did not interfere with clotting activity attributable to alpha-thrombin. Contrary to simple enzyme kinetics, velocities (reciprocal clotting times) were rectangular hyperbolically related to clotting activities. Clotting times between 5 and 90 s/clot correlated (r greater than 0.999) with reciprocal alpha-thrombin concentrations, permitting standardization with lyophilized plasma (1000 U.S. "NIH" thrombin-clotting units/L corresponded to approximately 21 s/clot with these plasma). Lyophilized plasma re-examined after 15 months displayed no change in clottability.
在98至2900纳摩尔/升范围内，凝血酶诱导的凝血时间与纤维蛋白原浓度成反比；这些倒数速度测量值的单位是秒/凝块。通过与经典酶动力学类比，我们定义了矩形双曲线参数，其中Km（凝块）范围为0.14至0.56微摩尔/升，k凝块为每秒0.020至0.075凝块。特异性比率（k凝块/Km（凝块））表明，重构的冻干人血浆作为可凝纤维蛋白原的来源，即使不比纯化蛋白本身更好，也同样良好。这些比率还表明，人酶中大于98%的自蛋白水解形式（β-和γ-凝血酶）的存在并不干扰α-凝血酶的凝血活性。与简单酶动力学相反，速度（倒数凝血时间）与凝血活性呈矩形双曲线关系。5至90秒/凝块之间的凝血时间与α-凝血酶浓度的倒数相关（r大于0.999），允许用冻干血浆进行标准化（1000美国“NIH”凝血酶-凝血单位/升对应于这些血浆约21秒/凝块）。15个月后重新检测的冻干血浆的可凝性没有变化。
