STUDIES ON FACTOR-XII IN PORCINE PLASMA - PURIFICATION AND ITS CONVERSION TO ACTIVATED FORM BY PORCINE PLASMA KALLIKREIN

When porcine plasma was subjected to four steps of ion-exchange column chromatographies, factor XII (F. XII) was separated into two fraction s, F. XII-1 and F. XII-2, and about 8.5 mg of F. XII-1 and 2.3 mg of F . XII-2 were obtained from 675 ml of the plasma. The purified proteins were found to give a single band on sodium dodecyl sulfate-polyacryla mide gel electrophoresis (SDS-PAGE). The molecular masses of F. XII-1 and XII-2 were estimated to be about 84 kDa by SDS-PAGE, and consisted of a single polypeptide chain. However, F. XII-1 converted to active form after removing Polybrene (R), but F. XII-2 was not activated. Act ivation of F. XII-2 took place on incubation with porcine plasma kalli krein, and the activation rate was increased only in the presence of n egatively charged surfaces, such as sulfatide. When the preparation wa s incubated with sulfatide, spontaneous activation was not observed on the condition that we used. Activation of porcine F. XII-2 by porcine plasma kallikrein was found to involve the cleavage of the peptide bo nd on the disulfide-bridged polypeptide chain, and further fragmentati on of activated form was observed during prolonged incubation time.