Lollar P, MacIntosh S C, Owen W G
J Biol Chem. 1984 Apr 10;259(7):4335-8.
A recirculating perfused rabbit heart preparation is used to study the reaction of antithrombin III (ATIII) with thrombin bound to the surface of the microvascular endothelium. Addition of ATIII to the system after thrombin is equilibrated with its binding sites results in inhibition of the enzyme as measured by disappearance of thrombin enzymatic activity from the circulation or by appearance of 125I-thrombin-ATIII complexes. The rate of inhibition of thrombin as reflected by either method is independent of the bound state of thrombin. Comparable results are obtained with ATIII modified at a single tryptophan residue. This modification does not alter the reaction rate of ATIII with thrombin but abolishes the capacity of heparin or heparan sulfate to enhance the reaction rate. From the kinetics and structural studies and the fit of the kinetics to a theoretical model relating binding equilibrium to thrombin inhibition, it is concluded that glycosaminoglycans are not involved in the reversible, high affinity, high capacity binding of thrombin to the vascular endothelium.
采用循环灌注兔心制备方法，研究抗凝血酶III（ATIII）与结合于微血管内皮表面的凝血酶的反应。凝血酶与其结合位点达到平衡后，向系统中加入ATIII，可使酶受到抑制，这可通过循环中凝血酶酶活性的消失或125I - 凝血酶 - ATIII复合物的出现来衡量。两种方法所反映的凝血酶抑制速率均与凝血酶的结合状态无关。用单个色氨酸残基修饰的ATIII也可得到类似结果。这种修饰不会改变ATIII与凝血酶的反应速率，但会消除肝素或硫酸乙酰肝素增强反应速率的能力。从动力学和结构研究以及动力学与将结合平衡与凝血酶抑制相关联的理论模型的拟合情况来看，得出的结论是，糖胺聚糖不参与凝血酶与血管内皮的可逆、高亲和力、高容量结合。
