Disulfide bond cleavage of human fibrinogen by cis-diamminedichloroplatinum(II)

Disulfide bridges in fibrinogen (Fbg) were cleaved by cis-diamminedichloroplatinum(II) (cis-DDP). Incubation with 120 molar excess of cis-DDP at pH 7.4 and 37 degrees C in the presence of EDTA resulted in cleavage of seven disulfide bridges out of 29. In the presence of calcium, however, the number of cleavages were reduced to four. The result indicates that calcium, which has three high affinity sites on Fbg, protects disulfide bridges from the rupture. Thrombin clottability was examined by turbidity measurement. The cis-DDP treated Fbg was shown to give a decreased fiber thickness. As the cleavage proceeded, the clotting ability of Fbg decreased.