| Celiac Sprue is an autoimmune disease of the small intestine caused by the ingestion of gluten proteins from widely prevalent food sources such as wheat, rye and barley. The symptoms include fatigue, diarrhea, anemia and neurological symptoms. Celiac Sprue is a lifelong disease, and if untreated it is associated with increased mortality. Despite its high prevalence in most populations (>1:200) and serious manifestations, the only effective therapy is strict dietary abstinence from these foodgrains.; In an attempt to elucidate the toxic components of gluten generated under physiological conditions, a 33-mer peptide LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF was identified that has several characteristics suggesting it is a major antigen of the inflammatory response to gluten. In vitro and in vivo studies in rats and humans demonstrated that it is stable toward breakdown by gastric, pancreatic, and intestinal brush-border membrane proteases. The peptide reacted with tissue transglutaminase with greater selectivity than known natural substrates. It was a potent inducer of gut-derived human T cell lines from all tested Celiac Sprue patients. The peptide could be detoxified by a bacterial prolyl endopeptidase, suggesting a strategy for oral peptidase supplement therapy for Celiac Sprue.; Based on the potential of prolyl endopeptidases to treat Celiac Sprue, the properties of three homologous bacterial prolyl endopeptidases were compared, from Flavobacterium meningosepticum, Sphingomonas capsulata and Myxococcus xanthus. These enzymes were assayed with chromogenic substrates and related gluten peptides important in Celiac Sprue pathogenesis. In vitro and in vivo studies were conducted to evaluate their activity, specificity and acid/protease stability. The enzymes exhibited substantial differences with respect to chain length and subsite specificity.; To further understand the molecular mechanisms of the enzymes, the crystal structures of two didomain PEPs have been solved in alternative configurations, providing fundamentally new insights into the mode of action of these enzymes. Comparative analysis of the two structures highlighted a critical role for the domain interface in regulating inter-domain dynamics and substrate specificity. Structure-based mutagenesis of the M. xanthus PEP confirmed an important role for several interfacial residues. Our results provide a strong foundation for further optimization of its clinically useful features. |
