Mechanism of ancrod anticoagulation

Abstract

A B S T R A C T Fibrin formed in response to ancrod, reptilase, or thrombin was reduced by P-mercaptoethanol and examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It was found that ancrod progressively and totally digested the a-chains of fibrin monomers at sites different than plasmin; however, further digestion of fibrin monomers by either reptilase or thrombin was not observed. Highly purified ancrod did not activate fibrin-stabilizing factor (FSF); however, the reptilase preparation used in these experiments, like thrombin, activated FSF and thereby promoted cross-link formation. Fibrin, formed by clotting purified human fibrinogen with ancrod, reptilase, or thrombin for increasing periods of time in the presence of plasminogen, was incubated with urokinase and observed for complete lysis. Fibrin formed by ancrod was strikingly more vulnerable to plasmin digestion than was fibrin formed by reptilase or thrombin. The lysis times for fibrin formed for 2 hr by ancrod, reptilase, or thrombin were 18, 89, and 120 min, respectively.Evidence was also obtained that neither ancrod nor reptilase activated human plasminogen. These results indicate that fibrin formed by ancrod is not cross-linked and has significantly degraded a-chains; as expected, ancrodformed fibrin is markedly susceptible to digestion by plasmin.

Homocysteine and its thiolactone impair plasmin activity induced by urokinase or streptokinase in vitro

“…Then, after disconnecting a short peptide from N-terminus of B␤ chain, the molecule of fibrinogen is converted into intermediates X (about 250 kDa). After their asymmetrical cleavage of X two fragments D (100 kDa) and Y (150 kDa) are formed, then Y fragment is cleaved into fragments E and D [20,21]. The fibrinogen degradation products, that appeared on SDS-PAGE gels under reducing conditions during the time limited degradation of fibrinogen (0, 1, 15 and 30 min), are shown in Fig.…”

Ancrod and Fibrin Formation

“…While ancrod-induced fibrin generation is well known, the fibrin produced has usually been understood to be non-cross-linked, soluble, readily degraded, and rapidly removed from the circulation 9, 12 . Ancrod-induced insoluble fibrin has been previously described in a plasma-based in vitro system using ancrod at a concentration at least two to three orders of magnitude higher than was used in the current study 13 . For the present work, we used a concentration of ancrod comparable to that utilized in stroke clinical trials (DE Levy, unpublished observations).…”

Cleavage of fibrinogen by the human neutrophil neutral peptide-generating protease.

“…Plasmin-limited proteolytic digestion of fibrinogen is characterized by a number of cleavages in the carboxy-terminal portion of the Aa chain (23,24) and removal of about 40 residues from the amino-terminal portion of the B3 chain, including fibrinopeptide B (25), to yield fragment X (260,000-300,000 Mr), which exhibits prolonged thrombininduced clotting activity (26). Although the 310,000-325,000 Mr fragment obtained during neutral peptide-generating protease cleavage of fibrinogen was able to be coagulated, the 270,000-280,000 Mr derivative was not.…”