title: Catalytic activity of anti-thyroglobulin antibodies.
abstract: Thyroglobulin (Tg)-specific autoantibodies from a patient with Hashimoto's thyroiditis hydrolyzed radiolabeled Tg, shown by production of several smaller sized products on SDS electrophoresis gels. The apparent Km value for Tg was in the nanomolar range, a property typical of an Ab combining site. The Tg antibodies also hydrolyzed tripeptide-methylcoumarinamide (MCA) substrates with lower affinity, displaying a preference for Arg-MCA and Lys-MCA containing conjugates. The hydrolysis of one of these conjugates, Pro-Phe-Arg-MCA, was inhibited competitively by Tg, suggesting a catalytic site located in the Ab combining site. In control experiments, 1) the hydrolytic activities were removed by immunoadsorption with immobilized anti-human IgG; 2) IgG depleted of the Tg-specific Abs by affinity chromatography did not display Tg and Pro-Phe-Arg-MCA hydrolyzing activities; and 3) the peptide-MCA hydrolyzing activity tracked exactly with the 150-kDa IgG peak on a gel filtration column run in denaturing solvent (6 M guanidine chloride).
authors.affiliation: Department of Anesthesiology, University of Nebraska Medical Center, Omaha 68198.
authors.forename: L
authors.initials: L
authors.lastname: Li
authors.forename: S
authors.initials: S
authors.lastname: Paul
authors.forename: S
authors.initials: S
authors.lastname: Tyutyulkova
authors.forename: M D
authors.initials: MD
authors.lastname: Kazatchkine
authors.forename: S
authors.initials: S
authors.lastname: Kaveri
mesh_terms: D000595:Amino Acid Sequence; D017151:Antibodies, Catalytic / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000276:immunology; D013379:Substrate Specificity; D013954:Thyroglobulin / Q000276:immunology*; D013967:Thyroiditis, Autoimmune / Q000276:immunology
chemical_list: D017151:Antibodies, Catalytic; D001323:Autoantibodies; D009842:Oligopeptides; C006606:anti-thyroglobulin; D013954:Thyroglobulin