The plasmin digestion of factor XIII, preliminary report

The plasmin digestion of factor XIII in the plasma with congenital afibrinogenemia has been reported by Suzuki et al. (1967).The present investigation is attempted to obtain some new aspects in the biochamical changes of factor XIII during the degradation with plasmin. The authors advanced the polyacrylamide disc electrophoresis and the cross-immunoelectrophoresis with anti-factor XIII (A & S) serum for the detection of molecular change of factor XIII and our modified method for the assay of factor XIII activity. In summary, it is concluded that the process of plasmin digestion of factor XIII can be divied into three steps described below.The first step; the subunit A of factor XIII such as placental factor XIII is ready to get plasmin digestion following the decrease of amount and activity of subunit A.The second step; in the observation of the subunit A2S complex like plasma factor XIII, the subunit S portion in the complex is more readily affected by. the plasmin digestion than the subunit A of the complex. Therefore, it is assumed that the subunit S may be play a protective role against the plasmin attack on the subunit A of the subunit A2S complex.The third step; subunit A2S complex coexisting with fibrinogen or plasma protein is fairly stable on exposure to plasmin. According to the results mentioned above, the mechanism of the plasmin digestion of factor XIII becomes highly complex by the inhibitory effects of the combination with subumit S or plasma protain including fibrinogen.It may be tentatively explained that the decrease of the factor XIII in afibrinogemia and DIC may be due to the consumption of factor XIII during the process of blood coagulation, and the plasmin digestion of the subunit A in the tissues and in the plasma by the local or secondary fibrinolysis with diminished plasma fibrinogen concentration.