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Abstract
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.