Stabilization of alpha-1-proteinase inhibitor by citrate.

alpha 1-Proteinase inhibitor has potential therapeutic value in patients with chronic deficiency (which can lead to emphysema) and in acute adult respiratory distress syndrome. Pasteurization (10 h, 60 degrees C) can reduce the risk of hepatitis B; and addition of stabilizers to the inhibitor helps prevent the loss of biological activity which occurs during pasteurization. Denaturation during heating at several temperatures was studied, using high pressure liquid chromatography, differential scanning calorimetry, and elastase inhibitory capacity to measure the extent of denaturation. The presence of 0.5 M citrate increases the Arrhenius-type activation energy 3-fold, and the enthalpy of denaturation is increased by 3.5 kJ/mol (15 kcal/mol). The onset temperature of the endotherm is increased by more than 10 degrees C. The inhibitor is further stabilized by sucrose (O.5 g/ml). In the presence of both citrate and sucrose, samples of alpha 1-proteinase inhibitor retained almost full biological activity following pasteurization for 10 h at 60 degrees C; the heating conditions used to destroy hepatitis B infectivity of other plasma derivatives.