VonWillebrandfactorisabloodglycoproteininvolvedincoagulation.ItisdeficientordefectiveinvonWillebranddiseaseandisinvolvedinalargenumberofotherdiseases,includingthromboticthrombocytopenicpurpura,Heydessyndrome,andpossiblyhemolytic-uremicsyndrome.vWFisalargemultimericglycoproteinpresentinbloodplasmaandproducedconstitutivelyinendothelium（intheWeibel-Paladebodies）,megakaryocytes（α-granulesofplatelets）,andsubendothelialconnectivetissue.ThebasicvWFmonomerisa2050aminoacidprotein.VonWillebrandfactorisnotanenzymeandthereforehasnocatalyticactivity.Itsprimaryfunctionisbindingtootherproteins,particularlyFactorVIIIanditisimportantinplateletadhesiontowoundsites.
