Structural heterogeneity and functional differentiation: a rationale for glycosylation analysis of recombinant therapeutics.

Many secreted and membrane-bound proteins exhibit microheterogeneity, even after purification to 'homogeneity'. Posttranslational processing and modification, including glycosylation, often accounts for the observed heterogeneity. While microheterogeneity is traditionally viewed as a biochemical nuisance of little or no functional significance, the increasing weight of recent evidence suggests quite a different perspective: that structural heterogeneity, including microheterogeneity, can impart functional differentiation within the population and thus represents a sophisticated mechanism of biological control and functional diversification. Because of a presumed connection between functional attributes and clinical characteristics, this perspective is the fundamental rationale for the analysis of the glycosylation of proteins employed as therapeutic agents.