In vitro inactivation of plasma α₁-proteinase inhibitor by epoxides and 1,2-dihaloethanes

The inactivating effects of three epoxides and two dihaloethanes on the proteinase inhibitory activities of α₁-proteinase inhibitor, as well as those of the plasma itself, were investigated. All of the three epoxides (styrene oxide, ethylene oxide and propylene oxide), individually, inactivated the elastase inhibitory or trypsin inhibitory activity of proteinase inhibitor, and that of whole plasma. Styrene oxide is the most effective inactivator of either purified α₁-proteinase inhibitor or plasma, followed by ethylene oxide and propylene oxide in a decreasing order of potency. The dihaloethanes, 1,2-dichloroethane and 1,2-dibromoethane, also inactivated the proteinase inhibitory activities of α₁-proteinase inhibitor with the former being somewhat more effective than the latter. Concomitant modification of the amino group was also observed with these chemicals.