| Popis: |
The surface binding activity of human coagulation factor XII is independent of pH while its proteolytic breakdown decreases considerably on lowering the pH (Samuel, M. and Villanueva, G.B. (1992) Biophysical J. 61, 1895). In the present study we showed that the amidolytic activity of factor XII in the presence of a soluble surface, dextran sulfate (DS500; Mr 500,000) decreases on lowering the pH. Electrophoretic and ultraviolet difference spectral studies indicate that factor XII binding stoichiometry to DS500 is reduced to half at pH 5.3 when compared to that at pH 7.4. A model is presented to show the different interactions of factor XII with DS500 which explains its well known stability at low pH. |
