Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The specific plasminogen activator from Trimeresurus stejnegeri venom (TSV-PA) is a serine proteinase presenting 23% sequence identity with the proteinase domain of tissue type plasminogen activator, and 63% with batroxobin, a fibrinogen clotting enzyme from Bothrops atrox venom that does not activate plasminogen. TSV-PA contains six disulfide bonds and has been successfully overexpressed in Escherichia coli (Zhang, Y., Wisner, A., Xiong, Y. L., and Bon, C. (1995) J. Biol. Chem. 270, 10246-10255). To identify the functional domains of TSV-PA, we focused on three short peptide fragments of TSV-PA showing important sequence differences with batroxobin and other venom serine proteinases. Molecular modeling shows that these sequences are located in surface loop regions, one of which is next to the catalytic site. When these sequences were replaced in TSV-PA by the equivalent batroxobin residues none generated either fibrinogen-clotting or direct fibrinogenolytic activity. Two of the replacements had little effect in general and are not critical to the specificity of TSV-PA for plasminogen. Nevertheless, the third replacement, produced by the conversion of the sequence DDE 96a-98 to NVI, significantly increased the Km for some tripeptide chromogenic substrates and resulted in undetectable plasminogen activation, indicating the key role that the sequence plays in substrate recognition by the enzyme.
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PMID:Trimeresurus stejnegeri snake venom plasminogen activator. Site-directed mutagenesis and molecular modeling. 925 66

Trimeresurus stejnegeri venom which contains TSV-PA (a specific plasminogen activator sharing 60-70% sequence homology with venom fibrinogen-clotting enzymes), also possesses fibrinogen-clotting activity in vitro. A fibrinogen-clotting enzyme (stejnobin) has been purified to homogeneity by gel filtration and ion-exchange chromatography on a Mono-Q column. It is a single-chain glycoprotein with a mol. wt of 44,000. The NH2-terminal amino acid sequence of stejnobin shows great homology with venom fibrinogen-clotting enzymes and TSV-PA. Like TSV-PA, stejnobin was able to hydrolyse several chromogenic substrates. Comparative study of substrate specificities of stejnobin and other venom proteases purified in our laboratory was carried out on five chromogenic substrates. Stejnobin clotted human fibrinogen with a specific activity of 122 NIH thrombin-equivalent units/mg protein. However, stejnobin did not act on other blood coagulation factors, such as factor X, prothrombin and plasminogen. Diisopropyl fluorophosphate and phenylmethanesulfonyl fluoride inhibited its activity, whereas ethylenediamine tetracetic acid had no effect on it, indicating that it is a serine protease. Although stejnobin showed strong immunological cross-reaction with polyclonal antibodies raised against TSV-PA, it was interesting to observe that, unlike the case of TSV-PA, these antibodies did not inhibit the amidolytic and fibrinogen-clotting activities of stejnobin.
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PMID:Characterization of a fibrinogen-clotting enzyme from Trimeresurus stejnegeri venom, and comparative study with other venom proteases. 960 87

From the venom of Chinese green tree viper (Trimeresurus stejnegeri), three distinct fibrinogenolytic enzymes: stejnefibrase-1, stejnefibrase-2 and stejnefibrase-3, were purified by gel filtration, ion-exchange chromatography and reverse-phase high-performance chromatography (HPLC). SDS-PAGE analysis of those three enzymes showed that they consisted of a single polypeptide chain with mol. wt of 50000, 31000 and 32000, respectively. Like TSV-PA (a specific plasminogen activator) and stejnobin (a fibrinogen-clotting enzyme) purified from the same venom, stejnefibrase-1, -2 and -3 were able to hydrolyze several chromogenic substrate. On the other hand, different from TSV-PA and stejnobin, stejnefibrase-1, -2 and -3 did not activate plasminogen and did not possess fibrinogen-clotting activity. The three purified enzymes directly degraded fibrinogen to small fragments and rendered it unclottable by thrombin. Stejnefibrase-2 degraded preferentially Bbeta-chain while stejnefibrase-1 and -3 cleaved concomitantly Aalpha and Bbeta-chains of fibrinogen. None of these proteases degraded the gamma-chain of fibrinogen. When correlated with the loss of clottability of fibrinogen, the most active enzyme was stejnefibrase-1. The activities of the three enzymes were inhibited by phenylmethylsulfonyl fluoride (PMSF) and p-nitrophenyl-p-guanidinobenzoate (NPGB), indicating that like TSV-PA and stejnobin, they are venom serine proteases.
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PMID:Characterization of three fibrinogenolytic enzymes from Chinese green tree viper (Trimeresurus stejnegeri) venom. 963 65

Snake venom serine proteinases, which belong to the subfamily of trypsin-like serine proteinases, exhibit a high degree of sequence identity (60-66%). Their stringent macromolecular substrate specificity contrasts with that of the less specific enzyme trypsin. One of them, the plasminogen activator from Trimeresurus stejnegeri venom (TSV-PA), which shares 63% sequence identity with batroxobin, a fibrinogen clotting enzyme from Bothrops atrox venom, specifically activates plasminogen to plasmin like tissue-type plasminogen activator (t-PA), even though it exhibits only 23% sequence identity with t-PA. This study shows that TSV-PA, t-PA, and batroxobin are quite different in their specificity toward small chromogenic substrates, TSV-PA being less selective than t-PA, and batroxobin not being efficient at all. The specificity of TSV-PA, with respect to t-PA and batroxobin, was investigated further by site-directed mutagenesis in the 189-195 segment, which forms the basement of the S(1) pocket of TSV-PA and presents a His at position 192 and a unique Phe at position 193. This study demonstrates that Phe(193) plays a more significant role than His(192) in determining substrate specificity and inhibition resistance. Interestingly, the TSV-PA variant F193G possesses a 8-9-fold increased activity for plasminogen and becomes sensitive to bovine pancreatic trypsin inhibitor.
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PMID:The contribution of residues 192 and 193 to the specificity of snake venom serine proteinases. 1063 81

A fibrinogen-clotting enzyme designed as jerdonobin-II was isolated from the venom of Trimeresurus jerdonii. It differed in molecular weight and N-terminal sequence with the previously isolated jerdonobin, a thrombin-like enzyme from the same venom. The enzyme consists of a single polypeptide chain with molecular weights of 30,000 and 32,000 under non-reducing and reducing conditions, respectively. Jerdonobin-II showed weak fibrinogen clotting activity and its activity unit on fibrinogen was calculated to be less than one unit using human thrombin as standard. The precursor protein sequence of jerodonobin-II was deduced from cloned cDNA sequence. The sequence shows high similarity (identity=89%) to TSV-PA, a specific plasminogen activator from venom of T. stejnegeri. Despite of the sequence similarity, jerdonobin-II was found devoid of plasminogen activating effect. Sequence alignment analysis suggested that the replacement of Lys239 in TSV-PA to Gln239 in jerdonobin-II might play an important role on their plasminogen activating activity difference.
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PMID:Molecular characterization of a weak fibrinogen-clotting enzyme from Trimeresurus jerdonii venom. 1568 74

Venoms from Pseudechis species (Australian black snakes) within the Elapidae family are rich in anticoagulant PLA2 toxins, with the exception of one species (P. porphyriacus) that possesses procoagulant mutated forms of the clotting enzyme Factor Xa. Previously the mechanism of action of the PLA2 toxins' anticoagulant toxicity was said to be due to inhibition of Factor Xa, but this statement was evidence free. We conducted a series of anticoagulation assays to elucidate the mechanism of anticoagulant action produced by P. australis venom. Our results revealed that, rather than targeting FXa, the PLA2 toxins inhibited the prothrombinase complex, with FVa-alone or as part of the prothrombinase complex-as the primary target; but with significant thrombin inhibition also noted. In contrast, FXa, and other factors inhibited only to a lesser degree were minor targets. We quantified coagulotoxic effects upon human plasma caused by all nine anticoagulant Pseudechis species, including nine localities of P. australis across Australia, and found similar anticoagulant potency across all Pseudechis species, with greater potency in P. australis and the undescribed Pseudechis species in the NT. In addition, the northern localities and eastern of P. australis were significantly more potent than the central, western, and southern localities. All anticoagulant venoms responded well to Black Snake Antivenom, except P. colletti which was poorly neutralised by Black Snake Antivenom and also Tiger Snake Antivenom (the prescribed antivenom for this species). However, we found LY315920 (trade name: Varespladib), a small molecule inhibitor of PLA2 proteins, exhibited strong potency against P. colletti venom. Thus, Varespladib may be a clinically viable treatment for anticoagulant toxicity exerted by this species that is not neutralised by available antivenoms. Our results provide insights into coagulotoxic venom function, and suggest future in vivo work be conducted to progress the development of a cheaper, first-line treatment option to treat PLA2-rich snake venoms globally.
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PMID:Anticoagulant activity of black snake (Elapidae: Pseudechis) venoms: Mechanisms, potency, and antivenom efficacy. 3244 17