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