title: Heparin enhances the inhibition of factor Xa by protein C inhibitor in the presence but not in the absence of Ca2+.
abstract: Protein C inhibitor (PCI) is a versatile serine protease inhibitor with both pro- and anticoagulant and other properties. Interactions of certain ligands with PCI, including heparin, affect its specificity for proteases. In this study, heparin was found to enhance PCI inhibition of factor Xa up to 42-fold in the presence of a physiological Ca(2+) concentration, whereas no heparin-induced activation was observed in the absence of Ca(2+). These results thus show that factor Xa adds to the group of proteases whose inhibition by PCI is enhanced by heparin and that such inhibition contributes to the anticoagulant properties of PCI by a Ca(2+)-dependent mechanism.
authors.affiliation: Department of Medical Biochemistry and Microbiology, Uppsala University, Box 582, SE-751 23 Uppsala, Sweden.
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.forename: Anna S
authors.initials: AS
authors.lastname: Eriksson
authors.forename: Sophia
authors.initials: S
authors.lastname: Schedin-Weiss
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000502:physiology*; D002413:Cations, Divalent / Q000737:chemistry; D015951:Factor Xa / Q000378:metabolism; D065427:Factor Xa Inhibitors; D006493:Heparin / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D018046:Protein C Inhibitor / Q000737:chemistry / Q000502:physiology*; D013053:Spectrophotometry
chemical_list: D002413:Cations, Divalent; D065427:Factor Xa Inhibitors; D018046:Protein C Inhibitor; D006493:Heparin; D015951:Factor Xa; D002118:Calcium