Purification and properties of factor XIII from human placenta.

1. FXIII was isolated and purified over 4000 fold from human placenta to apparent electrophoretic homogeneity by a new procedure including ethanol precipitation. DEAE-Cellulose, molecular sieving on Sephacryl S-300 and Phenyl-Sepharose chromatography. 2. Its pI was about 5.1. Under appropriate conditions, the incubation of FXIII in the presence of thrombin did not lead to inactivation cut in the polypeptidic chain. 3. FXIII was also activated by CaCl2 and, in a lesser extent, by other divalent cations like SrCl2, BaCl2 or MgCl2. 4. The binding of calcium to FXIII exhibited a negative cooperativity. 5. The activity-pH curve of the calcium-activated enzyme did not appear very different from that of the thrombin-activated enzyme.