Discovery of a novel and rich source of gluten-degrading microbial enzymes in the oral cavity.

Abstract

BACKGROUND:

Celiac disease is a T cell mediated-inflammatory enteropathy caused by the ingestion of gluten in genetically predisposed individuals carrying HLA-DQ2 or HLA-DQ8. The immunogenic gliadin epitopes, containing multiple glutamine and proline residues, are largely resistant to degradation by gastric and intestinal proteases. Salivary microorganisms however exhibit glutamine endoprotease activity, discovered towards glutamine- and proline-rich salivary proteins. The aim was to explore if gliadins can serve as substrates for oral microbial enzymes.

METHODOLOGY/PRINCIPAL FINDINGS:

Proteolytic activity in suspended dental plaque was studied towards a) gliadin-derived paranitroanilide(pNA)-linked synthetic enzyme substrates b) a mixture of natural gliadins and c) synthetic highly immunogenic gliadin peptides (33-mer of α2-gliadin and 26-mer of γ-gliadin). In addition, gliadin zymography was conducted to obtain the approximate molecular weights and pH activity profiles of the gliadin-degrading oral enzymes and liquid iso-electric focusing was performed to establish overall enzyme iso-electric points. Plaque bacteria efficiently hydrolyzed Z-YPQ-pNA, Z-QQP-pNA, Z-PPF-pNA and Z-PFP-pNA, with Z-YPQ-pNA being most rapidly cleaved. Gliadin immunogenic domains were extensively degraded in the presence of oral bacteria. Gliadin zymography revealed that prominent enzymes exhibit molecular weights >70 kD and are active over a broad pH range from 3 to 10. Liquid iso-electric focusing indicated that most gliadin-degrading enzymes are acidic in nature with iso-electric points between 2.5 and 4.0.

CONCLUSIONS/SIGNIFICANCE:

This is the first reported evidence for gluten-degrading microorganisms associated with the upper gastro-intestinal tract. Such microorganisms may play a hitherto unappreciated role in the digestion of dietary gluten and thus protection from celiac disease in subjects at risk.

• Authors: Eva J Helmerhorst, Maram Zamakhchari, Detlef Schuppan, Frank G Oppenheim
• Journal: PloS one (PLoS One) Vol. 5 Issue 10 Pg. e13264 (Oct 11 2010) ISSN: 1932-6203 [Electronic] United States
• PMID: 20948997 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Enzymes
• Glutens
• Gliadin

Topics

• Amino Acid Sequence
• Chromatography, High Pressure Liquid
• Enzymes (chemistry, metabolism)
• Gliadin (metabolism)
• Glutens (metabolism)
• Hydrogen-Ion Concentration
• Hydrolysis
• Isoelectric Focusing
• Molecular Sequence Data
• Mouth (microbiology)
• Sequence Homology, Amino Acid
• Spectrometry, Mass, Electrospray Ionization
• Tandem Mass Spectrometry