Effect of SpeB and EndoS from Streptococcus pyogenes on human immunoglobulins

Abstract

Streptococcus pyogenes secretes a specific immunoglobulin G (IgG)-protease, SpeB, as well as the IgG glycan-hydrolyzing enzyme EndoS. Here we show that SpeB also degrades IgA, IgM, IgD, and IgE. We also show that EndoS only hydrolyzes the glycan moiety on native but not denatured IgG. Thus, SpeB has a broad immunoglobulin-degrading activity, while EndoS is highly specific for IgG.

FIG. 1

SpeB activity on human immunoglobulins. Purified SpeB was incubated with purified IgG, IgA, IgM, IgD, and IgE in the presence or absence of active SpeB, as indicated. LC, light chains; HC, heavy chains. An asterisk indicates the protein band excised for NH₂-terminal sequencing.

FIG. 2

EndoS activity on native and denatured human IgG. Purified human IgG was incubated at the indicated temperatures prior to incubation with purified rEndoS. Samples were separated by SDS–10% PAGE and stained with Coomassie blue (stain) or blotted to a membrane and analyzed using G. nivalis lectin (blot).