Preparation and characterization of a soluble dextran ?1 proteinase inhibitor complex

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Abstract
Purified human α1 proteinase inhibitor, a plasma glycoprotein with a molecular weight of 5.3 × 104 daltons and a major serine protease inhibitor has been covalently coupled to dextrans with molecular weights of 1.77 × 104 and 1.03 × 104 daltons. The coupled conjugates were soluble in aqueous medium and stable up to 6 months at +5°C. Increased moles of dextran/mole protein ratio during coupling resulted in progressive decreases of inhibitory capacity, immunogenicity, and the association constant (kassoc) between the enzyme and the inhibitor. Compared to the native protein, the soluble conjugates showed improved stability at pH 3.0 and heat stability at 60°C. At 60°C, no loss of inhibitory capacity has been seen up to 60 min for the conjugates during which time the native protein lost greater than 90% of its inhibitory capacity. The presence of antioxidant catalase was needed to prevent oxidative degradation by hydrogen peroxide.