STABILIZATION OF LYOPHILIZED PORCINE PANCREATIC ELASTASE

Porcine pancreatic elastase, a well-characterized serine protease, has been used as a model to assess the effects of excessive humidity on s olid-state stability of the lyophilized protein. Elastase lyophilized without excipients retained full activity immediately after freeze-dry ing but became denatured upon continued storage at 40-degrees-C, 75% r elative humidity. The extent of inactivation could be monitored throug h assays of amidolytic activity, as well as through changes in the cir cular dichroism (CD) and fluorescence spectra. Differential scanning c alorimetry (DSC) was employed as a means of screening potential stabil izing additives; based on the results, sucrose and dextran 40 were sel ected for further evaluation. Both additives were effective in prevent ing denaturation. Possible mechanisms or the denaturation and stabiliz ation of elastase are discussed.