title: Thrombospondin fragmentation by alpha-thrombin and resistance to gamma-thrombin.
abstract: In the presence of 2mM-Ca2+, alpha-thrombin slowly cleaved thrombospondin (Mr 180 000) into 150 000-Mr and 30 000-Mr fragments. In the absence of Ca2+, the platelet glycoprotein was progressively and completely hydrolysed by 3 units of the enzyme/ml to 130 000-Mr, 95 000-Mr and 65 000-Mr fragments. In contrast, the nonclotting enzyme form, gamma-thrombin, did not hydrolyse the platelet protein either in the presence or in the absence of Ca2+, even at 10-fold higher concentrations of enzyme. Protein-interacting regions removed from the catalytic site, like those required for fibrinogen recognition, are necessary for thrombin proteolysis of thrombospondin.
mesh_terms: D000818:Animals; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins; D006868:Hydrolysis; D007527:Isoenzymes; D010446:Peptide Fragments / Q000032:analysis; D013917:Thrombin; D019699:Thrombospondins
chemical_list: D006023:Glycoproteins; D007527:Isoenzymes; D010446:Peptide Fragments; D019699:Thrombospondins; D013917:Thrombin