Removal of proteases from DNase I by chromatography over agarose with covalently attached lima bean protease inhibitor

Lima bean protease inhibitor (LBI) can be convalently attached to agarose using the cyanogen bromide activation procedure. The LBI-agarose complex retains full capacity to inhibit chymotrypsin and 30% capacity to inhibit trypsin; the dissociation constant for chymotrypsin bound to LBI-agarose is 3.7 × 10^?6m. Bovine pancreatic deoxyribonuclease is contaminated by 3% by weight of chymotrypsin plus chymotrypsinogen. The contaminating proteases may be removed from DNase by sequential reaction with LBI-agarose followed by filtration. The most effective method for the removal of proteases from DNase is chromatography over LBI-agarose. DNase which has been chromatographed over LBI-agarose is at least ten times more stable than DNase prepared by earlier procedures.