Structural changes accompanying enzymatic activation of human Hageman factor

Abstract

The structure of Hageman factor, isolated from human plasma, was analyzed before and after enzymatic activation. The purified molecule is a single polypeptide chain of 80,000 mol. wt. sedimenting at 4.5 sec. An amino acid analysis was performed. the concentration of Hageman factor in normal human plasma was found to be 29 μg/ml with variation between individuals ranging from 15 to 47 μg/ml. Treatment of the molecule with kallikrein, plasmin, or trypsin resulted in cleavage at two primary sites, yielding fragments of 52,000, 40,000, and 28,000 mol. wt. No further changes occurred in the fragments with subsequent reduction. Prekallikrein activating ability was associated exclusively with the 28,000 moiety.