title: Identification of glycyrrhizin as a thrombin inhibitor.
abstract: Glycyrrhizin (GL), an anti-inflammatory compound isolated from Glycyrrhiza glabra, was identified as a new thrombin inhibitor: (a) It prolonged plasma recalcification and thrombin and fibrinogen clotting times, and (b) it inhibited thrombin-induced, but not collagen-, PAF- or convulxin-induced platelet aggregation. On the other hand, GL did not block thrombin's amidolytic activity upon S-2238. Furthermore, the fluorescence emission intensity of dansyl-thrombin was increased upon GL binding. Moreover, GL displaced hirudin as an inhibitor of thrombin-catalyzed hydrolysis of S-2238. Our data provide evidence that GL is a selective inhibitor of thrombin (the first one isolated from plants) that is able to exert its anti-thrombin action by interacting with the enzyme's anion binding exosite 1. A pharmacophoric search identified GL as a sialyl Lewis X (SLe[X]) mimetic compound able to inhibit selectin binding to SLe(X). However, SLe(X) did not affect thrombin clotting activities, which indicates a lack of its interaction with thrombin and distinguishes both molecules. It is suggested that the anti-inflammatory effect of GL may be due to its effective anti-thrombin action.
authors.affiliation: Department of Medical Biochemistry, ICB/CCS, Federal University of Rio de Janeiro, Brazil.
authors.forename: I M
authors.initials: IM
authors.lastname: Francischetti
authors.forename: R Q
authors.initials: RQ
authors.lastname: Monteiro
authors.forename: J A
authors.initials: JA
authors.lastname: Guimarães
authors.forename: B
authors.initials: B
authors.lastname: Francischetti
mesh_terms: D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D000991:Antithrombins / Q000494:pharmacology*; D001665:Binding Sites; D001777:Blood Coagulation / Q000187:drug effects; D004151:Dipeptides / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism; D005453:Fluorescence; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D006035:Glycyrrhiza / Q000737:chemistry; D019695:Glycyrrhizic Acid; D006629:Hirudins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009844:Oligosaccharides / Q000494:pharmacology; D010946:Plants, Medicinal; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011817:Rabbits; D000080506:Sialyl Lewis X Antigen; D013917:Thrombin / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D000925:Anticoagulants; D000991:Antithrombins; D004151:Dipeptides; D006629:Hirudins; D009844:Oligosaccharides; D010975:Platelet Aggregation Inhibitors; D000080506:Sialyl Lewis X Antigen; C021129:S 2238; D019695:Glycyrrhizic Acid; D005340:Fibrinogen; D013917:Thrombin; D006034:Glycyrrhetinic Acid