Isolation of vasoactive peptides from human fibrin and fibrinogen degraded by plasmin

Abstract

Human fibrin(ogen) was incubated for 60 min at pH 8.0 and at 37 °C in a clot-lysis system containing plasmin. The low molecular weight degradation products (lmw-fdp or LMW-FDP) thus formed were separated from the bulk of the material by membrane filtration. After concentration and subsequent chromatography on Bio-Gel P-6, the degradation products were separated into at least 12 distinct fractions of which 3 had permeability-increasing activity. The major active fraction was further separated into 8 subfractions by column zone electrophoresis; 2 had permeability-increasing and 2 had vasoconstrictor activity. These active fractions were further purified to a homogeneous state by electrophoresis at pH 1.9. The recovery of each active peptide was about 60 %. Both permeability-increasing factors, a pentapeptide (Ala 2, Pro, Lys, Arg) and an undecapeptide (Ser, Glx 3, Pro 2, Val, Leu, Trp, Lys 2) contain 2 basic amino acids per molecule while the vasoconstrictors contain only 1 each. This difference in composition might explain the differences in their physiological activity. Finally, the location of the active peptides in the fibrinogen molecule has been tentatively assigned on the basis of their amino acid composition and the known sequence of fibrinogen.