Han X, Fiehler R, Broze G J
Division of Hematology, Barnes-Jewish Hospital at Washington University School of Medicine, 216 South Kingshighway Boulevard, St. Louis, MO 63110, USA.
Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9250-5. doi: 10.1073/pnas.95.16.9250.
Human protein Z (PZ) is a 62,000-Mr, vitamin K-dependent plasma protein whose structure is similar to coagulation factors VII, IX, X, protein C, and protein S, but whose function is not known. The procoagulant activity of factor Xa in a one-stage plasma coagulation assay is reduced when factor Xa is first incubated with PZ. This apparent inhibitory effect is time dependent, requires the presence of calcium ions and procoagulant phospholipids (rabbit brain cephalin), and appears predominantly related to the incubation period of PZ with cephalin. In serum the initial rate of inhibition of factor Xa with calcium ions and cephalin also is enhanced in the presence PZ. A PZ-dependent protease inhibitor (ZPI) has been isolated from plasma. ZPI is a 72,000-Mr single-chain protein with an N-terminal amino acid sequence of LAPSPQSPEXXA (X = indeterminate) and an estimated concentration in citrate-treated plasma of 1.0-1.6 microg/ml. In systems using purified components, the factor Xa inhibition produced by ZPI is rapid (>95% within 1 min by coagulation assay) and requires the presence of PZ, calcium ions, and cephalin. The inhibitory process appears to involve the formation of a factor Xa-PZ-ZPI complex at the phospholipid surface.
人蛋白Z（PZ）是一种分子量为62,000的维生素K依赖性血浆蛋白，其结构与凝血因子VII、IX、X、蛋白C和蛋白S相似，但其功能尚不清楚。在一期血浆凝血试验中，当因子Xa先与PZ孵育时，其促凝活性会降低。这种明显的抑制作用具有时间依赖性，需要钙离子和促凝磷脂（兔脑脑磷脂）的存在，并且主要与PZ与脑磷脂的孵育时间有关。在血清中，在PZ存在的情况下，钙离子和脑磷脂对因子Xa的初始抑制速率也会增强。一种PZ依赖性蛋白酶抑制剂（ZPI）已从血浆中分离出来。ZPI是一种分子量为72,000的单链蛋白，其N端氨基酸序列为LAPSPQSPEXXA（X = 不确定），在枸橼酸盐处理的血浆中的估计浓度为1.0 - 1.6微克/毫升。在使用纯化成分的系统中，ZPI产生的因子Xa抑制作用迅速（通过凝血试验在1分钟内>95%），并且需要PZ、钙离子和脑磷脂的存在。抑制过程似乎涉及在磷脂表面形成因子Xa - PZ - ZPI复合物。
