Comparative effects of stabilizing additives on the rates of heat inactivation of recombinant human interferon alpha-2b in solution.

This study was aimed at the comparative evaluation of stabilizing additives used for the protection of the antiviral activity of interferon-alpha2b against thermal inactivation, at 60 degrees C. The comparative effects of amino acids, polyhydric alcohols, saccharides and nonionic surfactants were studied. All were effective. Representing the thermal inactivation process with first order kinetics, a maximal prolongation of antiviral activity half-life of 39-fold was achieved with the most effective procedure. Inactivation rate constants varied from (53.3+/-4.6)x10(-3) to (2.5+/-0.3)x10(-3) min(-1). Human serum albumin, nonionic surfactants and monosaccharides increased half-life values by 5-39-, 5-23-, 4-20-fold, respectively. Amino acids, polyhydric alcohols and disaccharides increased t(1/2) values by 4-11-, 2-8- and 3-8-fold, respectively. These data provide useful information for the selection of stabilizing additives for IFN-alpha2b formulations.

Purification and characterization of the D-hydantoinase from Bacillus circulans.

A D-hydantoinase (5,6-dihydropyrimidine amidohydrolase) was purified to homogeneity from Bacillus circulans. Purification of two hundred forty-three-fold was achieved with an overall yield of 12%. The relative molecular mass of the native enzyme is 212,000 and that of the subunit is 53,000. This enzyme is an acidic protein with an isoelectric point of 4.55. The enzyme is sensitive to thiol reagent and requires metal ions for its activity. The optimal conditions for the hydantoinase activity are pH 8.0-10.0 and a temperature of 75 degrees C. The enzyme is the most stable in a pH range of 8.5-9.5 and up to 60 degrees C. The enzyme is significantly stable not only at high temperatures but also on treatment with protein denaturant SDS. These remarkable properties are used for the purification procedure.