Studies on the chymotryptic inhibitor from Ascaris lumbricoides var. suum: Purification and properties

The chymotryptic inhibitor from Ascaris lumbricoides was purified by ammonium sulfate fractionation, DEAE-, and CM-cellulose chromatography. The chromatographic patterns indicated the existence of at least two different chymotryptic inhibitors that show approximately the same specific activity. Cellulose acetate electrophoresis showed the existence of three components having inhibitory activity against chymotrypsin. By gel filtration on a Sephadex G-75 column, a pooled fraction was shown to have a molecular weight of about 8600. The chymotryptic “inhibitor” was unaffected by 8 M urea and showed a fairly broad range of heat and pH stabilities. Inactivation by mercaptoethanol was reversible after dialysis and air reoxidation. The inhibitor protected the enzyme against the denaturing actions of both 5 M urea and temperature. Recovery of the two components of the enzyme-inhibitor complex, both in the active state, was attained even after the denaturing treatment referred to above. The molecular weight of the complex as estimated by gel filtration on Sephadex G-75 suggests a stoichiometry of 1:1.