Transglutaminases are calcium dependent enzymes which are involved in a variety of human disease conditions. Nine different isotypes of transglutaminases have been described including transglutaminase 2 (TG2) which is the most well characterised isotype. Transglutaminases possess a range of different catalytic activities including; the posttranslational modification of proteins by the formation of ɛ-(ƴ-glutamyl) lysine cross links between two or more proteins, the incorporation of polyamine into proteins and the deamidation of protein bound glutamine to glutamate. In coeliac disease the deamidating activity of TG2 in the intestinal lamina propria converts glutamine to glutamate in undigested gliadin peptides. This conversion elicits an immune response which causes the typical symptoms of coeliac disease. Currently the only treatment for coeliac disease is a gluten free diet. The TG2 inhibitors are the potential therapeutic agents against the coeliac disease however the current chemically synthesised TG2 inhibitors have toxicity problems. Moreover, the progress in the treatment of coeliac disease is hampered by no suitable animal model for coeliac disease and the lack of a suitable TG2 deamidation assay with which to test potential inhibitors. In this study, it was hypothesised that an optimised deamidation assay can help measure TG2 deamidating activity precisely and the TG2 inhibitors from the natural sources such as milk and garlic can be potential therapeutic agents against coeliac disease which would be less or non-toxic to human cell lines. Key results include the development of a sensitive fluorescence microplate assay to measure the ammonia release from Vicia faba seed storage proteins as an indicator of TG2 deamidating activity; the assay was validated using non-denaturing electrophoretic assay. Two novel TG2 peptide inhibitors from soya milk were isolated by chromatographic methods, both of which showed potent inhibition of guinea pig liver and human recombinant TG2 (in low nM range). Using HT29 cells the two peptides induced significant reduction of TG2 activity in situ. The study also identified a fraction from garlic with TG2 inhibition properties. In addition, three TG2 substrates (T complex protein 1 subunit alpha, prelamin-A/C and a heat shock cognate protein) were also identified in HT29 cells.