Carbohydrate on human factor VIII/von Willebrand factor. Impairment of function by removal of specific galactose residues.
Human factor VIII/von Willebrand factor protein containing 120 +/- 12 nmol of sialic acid and 135 +/- 13 nmol of galactose/mg of protein was digested with neuraminidase. The affinity of native factor VIII/von Willebrand factor and its asialo form for the hepatic lectin that specifically binds asialoglycoproteins was assessed from in vitro binding experiments. Native factor VIII/von Willebrand factor exhibited negligible affinity while binding of the asialo derivative was comparable to that observed for asialo-alpha1-acid glycoprotein. Incubation of asialo-factor VIII/von Willebrand factor with Streptococcus pneumoniae beta-galactosidase removed only 62% of the galactose but abolished binding to the purified hepatic lectin. When the asialo derivative was incubated with purified beta-D-galactoside alpha2 leads to 6 sialyltransferase and CMP-[14C]NeuAc, only 61% of the galactose incorporated [14C]NeuAc. From the known specificites of these enzymes, it is concluded that galactose residues important in lectin binding are present in a terminal Gal/beta1 leads to 4GlcNAc sequence on asialo-factor VIII/von Willebrand factor. The relative ristocetin-induced platelet aggregating activity of native, asialo-, and agalacto-factor VIII/von Willebrand factor was 100:38:12, respectively, while procoagulant activity was 100:100:103.
D000818:Animals; D001779:Blood Coagulation Factors / Q000502:physiology; D005169:Factor VIII / Q000502:physiology; D005690:Galactose; D006801:Humans; D005779:Immunodiffusion; D037102:Lectins; D008099:Liver; D009439:Neuraminidase; D010974:Platelet Aggregation; D011817:Rabbits; D012794:Sialic Acids / Q000032:analysis; D001616:beta-Galactosidase; D014841:von Willebrand Factor / Q000502:physiology
D001779:Blood Coagulation Factors; D037102:Lectins; D012794:Sialic Acids; D014841:von Willebrand Factor; D005169:Factor VIII; D009439:Neuraminidase; D001616:beta-Galactosidase; D005690:Galactose