Susceptibility to transglutaminase of gliadin peptides predicted by a mass spectrometry‐based assay

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Abstract
A peptidomics approach was developed to identify transglutaminase‐susceptible Q residues within a pepsin–trypsin gliadin digest. Based on tagging with a monodansylcadaverine fluorescent probe, six α/β‐, γ‐gliadin, and low molecular weight glutenin peptides were identified by nanospray tandem mass spectrometry. In functioning as an acyl acceptor, tissue transglutaminase was able to form complexes with the glutamine‐rich gliadin peptides, whereas by lowering pH, the peptides were deamidated by transglutaminase at the same Q residues, which were previously transamidated. The main common feature shared by the peptides was the consensus sequence Q‐X‐P. Our findings offer relevant information for the understanding of how dietary peptides interact with the host organism in celiac disease.