Corn Trypsin Inhibitor
Corn Trypsin Inhibitor (CTI) is a highly specific inhibitor of trypsin and Factor XIIa that does not affect Factors VIIa, IXa, Xa, or thrombin. CTI forms a one-to-one molar complex with target proteases and is useful for distinguishing between the intrinsic and extrinsic coagulation cascades. CTI is extracted from high quality sweet corn meal into a physiologic buffer then purified by a combination of gel filtration, ion-exchange, and affinity chromatography. The final CTI preparation appears as a single band by SDS-PAGE analysis under both reducing and non-reducing conditions. Preparations of CTI are tested for the ability to prolong the aPTT assay without affecting the PT assay. The specific activity of each lot of CTI is determined, and one unit is defined as the amount of CTI required to double the aPTT of normal human plasma.