WHEAT GAMMA GLIADIN AS SUBSTRATE FOR BOVINE PLASMA FACTOR-XIII

For the first time, a transglutaminase (EC 2.3.2.13) activity was investigated in water/solvent mixtures. This study highlighted that bovine plasma transglutaminase (factor XIII) was active in the presence of dioxane, acetonitrile, and ethanol up to 15%, 20%, and 20%, respectively. It allowed enzymatic modification of wheat prolamins. The transfer and hydrolytic activities of factor XIII were investigated on a purified gamma 46 gliadin considered as a prolamin model substrate. In optimum conditions of pH and dioxane concentration, 15% of the glutaminyl residues present in gamma gliadin were deamidated after 24 h of enzymatic treatment. The nonrepetitive region of the gamma gliadin was preferentially modified by factor XIII. The transglutaminase was able to produce soluble polymeric complexes of gliadins, through intermolecular epsilon-(gamma-glutamyl)lysyl cross-links. The two lysyl residues of gamma gliadin were supposed to act as acyl acceptor sites.