title: Evaluation of ADAMTS-13 activity in plasma using recombinant von Willebrand Factor A2 domain polypeptide as substrate.
abstract: The metalloprotease ADAMTS-13 cleaves von Willebrand factor (VWF), and is absent or severely reduced in the plasma of patients with thrombotic thrombocytopenia purpura (TTP). Under physiologic flowing conditions, the enzyme cleaves endothelial cell-derived ultra-large VWF multimers at the Y842/M843 peptide bond located in the A2 domain, where many mutations associated with Type 2A VWD cluster. These VWF mutants are more susceptible for cleavage activity, decreasing the large VWF multimers in the plasma. The susceptibility of a recombinant VWF-A2 domain to ADAMTS-13 and the potential application in detecting enzyme activity were investigated. In vitro, fluid phase cleavage of VWF by ADAMTS-13 requires denaturing conditions and prolonged incubation in order to estimate enzyme activity. We have measured ADAMTS-13 activity based on enzyme cleavage of a recombinant VWF-A2 domain under non-denaturing conditions. In our assay, enzyme activity was absent in plasma from congenital and acquired TTP patient, and blocked by each EDTA, monoclonal antibody VP-1 (peptide-specific antibody against residues 828-842 of VWF), and an ADAMTS-13 antibody purified from plasma of an acquired TTP patient. This novel recombinant VWF-A2 protein has potential utility as matrix for a rapid clinical measurement of plasma ADAMTS-13 activity.
authors.affiliation: Thrombosis Research Section, Department of Medicine, Baylor College of Medicine, One Baylor Plaza, N1319, Houston, Texas 77030, USA. MIGUELC@BCM.TMC.EDU
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Cruz
authors.forename: Jody
authors.initials: J
authors.lastname: Whitelock
authors.forename: Jing-fei
authors.initials: JF
authors.lastname: Dong
mesh_terms: D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001323:Autoantibodies / Q000494:pharmacology; D016022:Case-Control Studies; D003001:Cloning, Molecular; D004492:Edetic Acid / Q000494:pharmacology; D006801:Humans; D007118:Immunoassay; D008666:Metalloendopeptidases / Q000097:blood* / Q000276:immunology / Q000378:metabolism; D010446:Peptide Fragments; D017434:Protein Structure, Tertiary; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood; D011994:Recombinant Proteins; D014841:von Willebrand Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D001323:Autoantibodies; D010446:Peptide Fragments; D011994:Recombinant Proteins; D014841:von Willebrand Factor; D004492:Edetic Acid; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human