Fibrin Polymerization. 1. Alkylating peptide inhibitors of fibrin polymerization.
A series of analogues relating to the NH2-terminal region of the fibrin alpha chain, i.e., Gly-Pro-Arg-Pro, were prepared by stepwise solid-phase synthesis, and their abilities to inhibit fibrin polymerization and to prolong thrombin-initiated clotting time were evaluated. Among the analogues systematically modified at different positions, replacement of the NH2-terminal three residues of Gly-Pro-Arg-Pro by either chlorambucil, p-nitrophenyl-L-alanine, or p-aminophenyl-L-alanine gave inactive compounds in the thrombin time assay, whereas similar substitution or extension of the COOH terminus produced the highly active analogues Gly-Pro-Arg-Phe(4-NH2), 22%; Gly-Pro-Arg-Pro-Phe(4-NO2), and Gly-Pro-Arg-Pro-Phe(4-NH2), 105%; relative to Gly-Pro-Arg-Pro = 100% in the fibrin polymerization inhibitory assay. As potential photoaffinity labeling probes, analogues containing a nitrophenylalanine residue in position 4 or 5 underwent photolysis under the experimental photoactivation conditions. As a potential alkylating probe, Chl-Pro-Arg-Pro was selectively effective in inhibiting thrombin amidolysis and fibrin polymerization. In the latter assay, Chl-Pro-Arg-Pro was approximately 20 times more potent than Gly-Pro-Arg-Pro in inhibiting fibrin aggregation.
D000478:Alkylation; D000925:Anticoagulants / Q000494:pharmacology*; D001665:Binding Sites; D005337:Fibrin / Q000378:metabolism*; D006801:Humans; D010455:Peptides / Q000494:pharmacology*; D010782:Photolysis; D011108:Polymers / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013917:Thrombin / Q000378:metabolism
D000925:Anticoagulants; D010455:Peptides; D011108:Polymers; D005337:Fibrin; D013917:Thrombin