Inhibition of thrombin and other trypsin-like serine proteinases by cyclotheonamide A. 1993

S D Lewis, and A S Ng, and J J Baldwin, and N Fusetani, and A M Naylor, and J A Shafer
Department of Biological Chemistry, Merck Research Laboratories, West Point, Pennsylvania 19486.

Cyclotheonamide A (CA), a cyclic peptide isolated from the marine sponge of the genus Theonella was shown to be a slow-binding inhibitor of several trypsin-like serine proteinases. Values of 4.6 x 10(4), 4.8 x 10(4), 9.3 x 10(3), 2.1 x 10(3) and 2.7 x 10(2) M-1 s-1 were determined for the second-order rate constants for formation of CA complexes with thrombin, trypsin, plasmin, 2-chain t-PA and factor Xa, respectively. The equilibrium constant (Ki) was measured for dissociation of CA from the CA complex with human thrombin (Ki = 1.0 nM), bovine trypsin (Ki = 0.2 nM), human plasmin (Ki = 12 nM), human factor Xa (Ki = 50 nM) and human 2-chain tissue plasminogen activator (t-PA) (Ki = 40 nM). CA produces dose dependent increases in clotting time assays. The clotting time in the thrombin time, activated partial thromboplastin time and prothrombin time assays, were doubled by 1.5, 0.9 and 48 microM CA, respectively. A model for the binding of CA to the active site of thrombin is proposed.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008954 Models, Biological Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment. Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D008958 Models, Molecular Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures. Molecular Models,Model, Molecular,Molecular Model
D010456 Peptides, Cyclic Peptides whose amino acid residues are linked together forming a circular chain. Some of them are ANTI-INFECTIVE AGENTS; some are biosynthesized non-ribosomally (PEPTIDE BIOSYNTHESIS, NON-RIBOSOMAL). Circular Peptide,Cyclic Peptide,Cyclic Peptides,Cyclopeptide,Orbitide,Circular Peptides,Cyclopeptides,Orbitides,Peptide, Circular,Peptide, Cyclic,Peptides, Circular
D010959 Tissue Plasminogen Activator A proteolytic enzyme in the serine protease family found in many tissues which converts PLASMINOGEN to FIBRINOLYSIN. It has fibrin-binding activity and is immunologically different from UROKINASE-TYPE PLASMINOGEN ACTIVATOR. The primary sequence, composed of 527 amino acids, is identical in both the naturally occurring and synthetic proteases. Alteplase,Plasminogen Activator, Tissue-Type,T-Plasminogen Activator,Tissue-Type Plasminogen Activator,Actilyse,Activase,Lysatec rt-PA,TTPA,Tisokinase,Tissue Activator D-44,Lysatec rt PA,Lysatec rtPA,Plasminogen Activator, Tissue,Plasminogen Activator, Tissue Type,T Plasminogen Activator,Tissue Activator D 44,Tissue Type Plasminogen Activator
D011485 Protein Binding The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments. Plasma Protein Binding Capacity,Binding, Protein
D001780 Blood Coagulation Tests Laboratory tests for evaluating the individual's clotting mechanism. Coagulation Tests, Blood,Tests, Blood Coagulation,Blood Coagulation Test,Coagulation Test, Blood,Test, Blood Coagulation
D005341 Fibrinolysin A product of the lysis of plasminogen (profibrinolysin) by PLASMINOGEN activators. It is composed of two polypeptide chains, light (B) and heavy (A), with a molecular weight of 75,000. It is the major proteolytic enzyme involved in blood clot retraction or the lysis of fibrin and quickly inactivated by antiplasmins. Plasmin,Fibrogammin,Glu-Plasmin,Protease F,Thrombolysin,Glu Plasmin
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001665 Binding Sites The parts of a macromolecule that directly participate in its specific combination with another molecule. Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining

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