[28] Characterization of recombinant proteins

This chapter discusses characterization of recombinant proteins. The therapeutic utility of a recombinant protein is profoundly influenced by its macromolecular structure. The structural features that influence biological response may vary widely depending on the cell type used as the host expression system and the conditions under which the protein is expressed. Variation in biological response (in vitro or in vivo) may be attributed to the primary structure of the protein or to posttranslational modification or processing by the host expression system. Indeed, even within a specific cell line, a number of physiological and nonphysiological conditions influence the extent and type of posttranslational processing, and, hence, the therapeutic utility of the expressed protein. In order to better understand the functional implications of structural variation, it is important to assess in detail the structural features of recombinant proteins. These structural features include both host-specific modifications (e.g., glycosylation, acylation, and phosphorylation) and those that may be induced during expression or purification (e.g., oxidation, deamidation, and N- and C-terminal heterogeneity).