title: Protein Z circulates in plasma in a complex with protein Z-dependent protease inhibitor.
abstract: Protein Z (PZ) is a vitamin K-dependent plasma protein that forms a Ca++-dependent complex with factor Xa at phospholipid surfaces. This interaction between PZ and factor Xa enhances by >1,000-fold the inhibition of factor Xa by the serpin called protein Z-dependent protease inhibitor (ZPI). These experiments show that PZ also binds ZPI in a process that does not require Ca++ or phospholipids. In pooled normal plasma, which contains excess ZPI relative to PZ, all the PZ appears to be bound in a complex with ZPI. The binding of PZ to ZPI reduces the rate and extent of factor XIa inhibition produced by ZPI. During the course of these studies, it was noted that a PZ purification procedure, that included NaSCN (2.0 M) elution of PZ from an immunoaffinity column, produced aggregated, inactive forms of PZ.
authors.affiliation: Division of Hematology, Barnes-Jewish Hospital at Washington University Medical Center, St Louis, MO 63110, USA.
authors.forename: A
authors.initials: A
authors.lastname: Tabatabai
authors.forename: R
authors.initials: R
authors.lastname: Fiehler
authors.forename: G J
authors.initials: GJ
authors.lastname: Broze
mesh_terms: D001797:Blood Protein Electrophoresis; D001798:Blood Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D015945:Factor XIa / Q000037:antagonists & inhibitors; D006801:Humans; D046911:Macromolecular Substances; D011485:Protein Binding; D011487:Protein Conformation; D015843:Serpins / Q000097:blood* / Q000737:chemistry
chemical_list: D001798:Blood Proteins; D046911:Macromolecular Substances; C416370:SERPINA10 protein, human; D015843:Serpins; C026080:plasma protein Z; D015945:Factor XIa