肝素分子的多个功能域。
Multiple functional domains of the heparin molecule.
作者信息
Oosta G M, Gardner W T, Beeler D L, Rosenberg R D
出版信息
Proc Natl Acad Sci U S A. 1981 Feb;78(2):829-33. doi: 10.1073/pnas.78.2.829.
Affinity-fractionated porcine heparin was randomly scissioned by chemical techniques to give hexasaccharides, octasaccharides, decasaccharides, and mucopolysaccharide fragments of approximately 14 residues and approximately 16 residues that were able to complex with the protease inhibitor. Direct measurements of the kinetic behavior of the hexasaccharides, octasaccharides, and decasaccharides showed that these fractions greatly enhanced the rate of Factor Xa inactivation by antithrombin. Indeed, these species exhibited specific molar activities that ranged from 6.9% (hexaccharide) to 60.9% (decasaccharide) of that of the heparin fragment of approximately 16 residues. However, these oligosaccharides exhibited essentially no ability to accelerate thrombin-antithrombin interactions. The avidity of the hexasaccharides, octasaccharides, and decasaccharides for the protease inhibitor increased as a function of size with the respective dissociation constants ranging from 5.5 X 10(-6) M to 2.9 X 10(-7) M. These data suggest that the region of the heparin molecule needed for catalyzing Factor Xa-antithrombin interaction is intimately related to the antithrombin binding domain. The smallest complex carbohydrate fragment that accelerated the inactivation of thrombin by antithrombin had approximately 14 residues. This fraction had an avidity for the protease inhibitor of 2.8 X 10(-7) M and specific molar activities of 140 units per mumol (thrombin neutralization) and 460 units per mumol (factor Xa inactivation). The largest heparin fragment examined contained approximately 16 residues. This fraction had an avidity for antithrombin of 2.4 X 10(-7) M and specific molar activities of 500 units per mumol (thrombin neutralization) and 560 units per mumol (Factor Xa inactivation). Detailed kinetic analyses showed that these two species are able to directly activate antithrombin to the same extent with respect to thrombin inhibition. However, the larger mucopolysaccharide fragment is also capable of approximating free enzyme with protease inhibitor.
亲和分级分离的猪肝素通过化学技术随机断裂，得到六糖、八糖、十糖以及含有约14个残基和约16个残基的粘多糖片段，这些片段能够与蛋白酶抑制剂结合。对六糖、八糖和十糖的动力学行为进行直接测量表明，这些级分极大地提高了抗凝血酶使因子Xa失活的速率。实际上，这些物质的比摩尔活性范围为约16个残基的肝素片段的6.9%（六糖）至60.9%（十糖）。然而，这些寡糖基本上没有加速凝血酶 - 抗凝血酶相互作用的能力。六糖、八糖和十糖对蛋白酶抑制剂的亲和力随大小增加，各自的解离常数范围为5.5×10⁻⁶ M至2.9×10⁻⁷ M。这些数据表明，肝素分子中催化因子Xa - 抗凝血酶相互作用所需的区域与抗凝血酶结合域密切相关。加速抗凝血酶使凝血酶失活的最小复合碳水化合物片段含有约14个残基。该级分对蛋白酶抑制剂的亲和力为2.8×10⁻⁷ M，比摩尔活性为每微摩尔140单位（凝血酶中和）和每微摩尔460单位（因子Xa失活）。检测的最大肝素片段含有约16个残基。该级分对抗凝血酶的亲和力为2.4×10⁻⁷ M，比摩尔活性为每微摩尔500单位（凝血酶中和）和每微摩尔560单位（因子Xa失活）。详细的动力学分析表明，就凝血酶抑制而言，这两种物质能够在相同程度上直接激活抗凝血酶。然而较大的粘多糖片段也能够使游离酶与蛋白酶抑制剂接近。
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