Samuel E, Samuel M, Villanueva G B
Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla 10595-1690.
Biochem Mol Biol Int. 1994 Aug;33(5):827-34.
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.
人凝血因子XII的表面结合活性与pH无关，而其蛋白水解降解在降低pH时会显著减少（塞缪尔，M.和维拉纽瓦，G.B.（1992年）《生物物理杂志》61卷，第1895页）。在本研究中，我们表明在存在可溶性表面硫酸葡聚糖（DS500；分子量500,000）的情况下，因子XII的酰胺水解活性会随着pH降低而降低。电泳和紫外差光谱研究表明，与pH 7.4时相比，在pH 5.3时因子XII与DS500的结合化学计量比降低至一半。本文提出了一个模型，以展示因子XII与DS500的不同相互作用，这解释了其在低pH下众所周知的稳定性。
