Tollefsen D M, Majerus D W, Blank M K
J Biol Chem. 1982 Mar 10;257(5):2162-9.
We have isolated a previously unrecognized heparin-dependent inhibitor of thrombin from human plasma. The inhibitor, designated heparin cofactor II (HCII), was purified to homogeneity with sulfated-dextran, DEAE-Sepharose, heparin-Sepharose and Sephadex G-150. HCII is a glycoprotein consisting of a single polypeptide chain with a Mr = 65,600 as determined by sedimentation equilibrium analysis. Other physical properties include s20,w = 4.31 S; Stokes radius = 34 A; E280 1% = 11.7; and pI = 4.95 to 5.15. The purified inhibitor is not precipitated by antibodies directed against seven other plasma protease inhibitors, including antithrombin III (ATIII). HCII blocks the proteolytic and amidolytic activities of thrombin by forming a covalent, 1:1 molar complex with the protease. The second-order rate constant for inhibition of thrombin by purified HCII increases from 5.0 X 10(5) M-1 min-1 in the absence of heparin to 4.5 x 10(8) M-1 min-1 at optimal heparin concentrations of 0.8 to 1.0 unit/ml. In comparison with ATIII, HCII is a relatively ineffective inhibitor of coagulation factor Xa.
我们从人血浆中分离出一种以前未被识别的凝血酶肝素依赖性抑制剂。该抑制剂被命名为肝素辅因子II（HCII），通过硫酸葡聚糖、二乙氨基乙基琼脂糖凝胶（DEAE - Sepharose）、肝素琼脂糖凝胶（heparin - Sepharose）和葡聚糖凝胶G - 150纯化至同质。通过沉降平衡分析确定，HCII是一种糖蛋白，由一条单多肽链组成，相对分子质量为65,600。其他物理性质包括：沉降系数s20,w = 4.31 S；斯托克斯半径 = 34 Å；在280 nm波长下的吸光系数E280 1% = 11.7；等电点pI = 4.95至5.15。纯化后的抑制剂不会被针对其他七种血浆蛋白酶抑制剂（包括抗凝血酶III（ATIII））的抗体沉淀。HCII通过与蛋白酶形成1:1摩尔比的共价复合物来阻断凝血酶的蛋白水解和酰胺水解活性。纯化的HCII对凝血酶抑制作用的二级速率常数在无肝素时为5.0×10⁵ M⁻¹ min⁻¹，在最佳肝素浓度0.8至1.0单位/毫升时增加到4.5×10⁸ M⁻¹ min⁻¹。与ATIII相比，HCII是凝血因子Xa相对低效的抑制剂。
