Terminal plasmin degradation products D and E of duck fibrinogen and their effect on polymerization of fibrin.

Duck fibrinogen (Mr 320 000) treated with streptokinase-activated human plasminogen in the presence of calcium ions was hydrolysed to terminal core fragments D and E. They were isolated from the digest by: (1) ion-exchange chromatography on DEAE-cellulose, (2) gel filtration on Sephadex G-100, and (3) affinity chromatography with the use of fibrin monomers coupled to CNBr-activated Sepharose. When the native D fragment, D1 was additionally digested by plasmin in the presence of EDTA, more degraded forms D2 and D3 appeared. Molecular weight of D1, D2, D3 and E estimated on SDS-polyacrylamide gel electrophoresis is 100 000, 89 000, 80 000 and 50 000, respectively. It was found that after reduction with 2-mercaptoethanol the fragments D1 and D3 consisted each of three polypeptide chains: alpha, beta, gamma: the gamma-chain of D3 remnant was more degraded (Mr 24 000) as compared with the gamma-chain of D1 remnant (Mr 42 000). Polymerization of both duck and pig fibrin monomers was inhibited by fragments D1 but not by D3.