Protein Z

protein Z
Crystallographic structure protein Z.
Identifiers
Symbol	PROZ
Entrez	8858
HUGO	9460
OMIM	176895
PDB	1LP1
RefSeq	NM_003891
UniProt	P22891
Other data
Locus	Chr. 13 q34

Protein Z (PZ or PROZ) is a protein which in humans is encoded by the PROZ gene.

Protein Z is a member of the coagulation cascade, the group of blood proteins that leads to the formation of blood clots. It is a gla domain protein and thus vitamin K-dependent, and its functionality is therefore impaired in warfarin therapy. It is a glycoprotein.

Although it is not enzymatically active, it is structurally related to several serine proteases of the coagulation cascade: factors VII, IX, X and protein C. The carboxyglutamate residues (which require vitamin K) bind protein Z to phospholipid surfaces.

The main role of protein Z appears to be the degradation of factor Xa. This is done by protein Z-related protease inhibitor (ZPI), but the reaction is accelerated 1000-fold by the presence of protein Z. Oddly, ZPI also degrades factor XI, but this reaction does not require the presence of protein Z.

In some studies, deficiency states have been associated with a propensity to thrombosis. Others, however, link it to bleeding tendency; there is no clear explanation for this, as it acts physiologically as an inhibitor, and deficiency would logically have led to a predisposition for thrombosis.

It is 62 kDa large and 396 amino acids long. The PROZ gene has been linked to the thirteenth chromosome (13q34).