Immunoglobulin-degrading enzyme of Streptococcus equi (IdeE)

Immunoglobulin-degrading enzyme of Streptococcus equi (IdeE) is a specialized cysteine protease secreted by the bacterium Streptococcus equi, the causative agent of strangles, a highly contagious and severe respiratory disease in horses. The enzyme's primary biological function is the site-specific cleavage of the heavy chains of equine immunoglobulin G (IgG) within the hinge region (Hulting et al., 2009, FEMS Microbiol Lett). This proteolytic activity effectively uncouples the antigen-recognition domain from the effector domain, neutralizing the host's ability to clear the bacteria through opsonophagocytosis or complement activation (Boyle et al., 2011, Vet Microbiol). By degrading these essential immune components, IdeE serves as a critical virulence factor that facilitates bacterial evasion of the host's humoral immune response. In the field of veterinary medicine, IdeE is a major target for vaccine development and is a key antigenic component of the multi-component recombinant vaccine Strangvac (Robinson et al., 2020, Vaccine). While it is a homolog of the human-targeted enzyme IdeS (Imlifidase), IdeE is evolutionarily specialized for the equine immune system, making it a distinct target for preventing streptococcal infections in animal populations (UniProtKB B1I9I1). Understanding the structure and function of IdeE is essential for the design of next-generation anti-infectives and diagnostic tools for equine health.

Other names

IdeEIgG-degrading enzyme of S. equiMac-1-like proteinEndopeptidase IdeEStreptococcus equi endopeptidase

IdeE functions as a highly specific endopeptidase that cleaves the hinge region of equine immunoglobulin G (IgG) heavy chains, specifically targeting subclasses IgG1, IgG4, and IgG7. This cleavage separates the antigen-binding Fab fragments from the effector Fc region, thereby neutralizing antibody-mediated immune responses such as opsonization and complement-dependent cytotoxicity (Hulting et al., 2009, FEMS Microbiol Lett; Robinson et al., 2020, Vaccine).