Introduction
Protein Z (PZ) is a 62 kDa vitamin K-dependent plasma glycoprotein consisting of 360 amino acids in the mature protein (1-3). Protein Z circulates as a cofactor of the PZ-dependent inhibitor (ZPI) to accelerate the inhibition of activated factor X on phospholipid surfaces (4). Protein Z appears to assist hemostasis by binding thrombin and promoting its association with phospholipid vesicles. Protein Z deficiency may induce bleeding as well as thrombosis (5). Protein Z deficiency could be a risk for venous and arterial thrombosis and early fetal loss. Protein Z and/or ZPI are synthesized by normal kidney and different cancer cells, suggesting that the complex PZ/ZPI could play a role in inhibiting the tissue deposition of fibrin (6).

Principle of the Assay
The AssayMax Human Protein Z ELISA (Enzyme-Linked Immunosorbent Assay) kit is designed for detection of human protein Z in plasma, serum, urine, milk, and cell culture samples. This assay employs a quantitative sandwich enzyme immunoassay technique that measures human protein Z in less than 4 hours. A polyclonal antibody specific for human protein Z has been pre-coated onto a 96-well microplate with removable strips. Protein Z in standards and samples is sandwiched by the immobilized antibody and the biotinylated polyclonal antibody specific for protein Z, which is recognized by a streptavidin-peroxidase conjugate. All unbound material is then washed away and a peroxidase enzyme substrate is added. The color development is stopped and the intensity of the color is measured.