FIGURE 6.

Partial deglycosylation sensitizes SIgA to proteolysis. Human SIgA was gently N-deglycosylated with N-glycanase without detergent or reducing agent or mock treated with buffer without glycosidase enzyme, followed by exposure to a range of protease concentrations. A, subtilisin more readily cleaves a partially N-glycosylated SIgA substrate within the secretory component. Fluorescein-labeled SIgA (0.2 mg/ml) was treated with and without N-glycanase in the presence of Nonidet P-40. The partially N-deglycosylated SIgA secretory component runs at a lower molecular mass. Deglycosylation results in acceleration of proteolysis of the secretory component by subtilisin at 0.05–2 μg/ml. B, quantification of SC bands shows that partially deglycosylated secretory component is proteolyzed with about 10 times less protease.