Synthesis and characterization of a water‐soluble affinity polymer for trypsin purification

A specific ligand bound polymer has been synthesized for the purpose of purification and stabilization of trypsin, an easily autodigestible enzyme. The affinity polymer was formed by copolymerizing N‐acryloyl‐m‐aminobenzamidine, a strong trypsin inhibitor, and acrylamide in the absence of oxygen. Kinetic studies on the trypsin inhibition revealed that there was a strong binding between this enzyme and the polymer and the mechanism was of a competitive manner with an inhibition constant of 0.6 × 10⁻³M. Such an affinity polymer was also very effective in preventing trypsin from auto‐digestion at 4°C. Based on this finding and the principle of cross flow filtration, a new process has been developed for purification of trypsin from a solution containing chymotrypsin. The experimental data indicated that trypsin was bound to the polymer (MW > 10⁵) and remained in the retentate while unbound chymotrypsin was collected in the filtrate. This purification process has a capability of recovering 98% pure trypsin at 90% yield.