Investigations of conformational structures and activities of trypsin and pepsin affected by food colourant allura red

Abstract

Herein, binding interactions of food colourant allura red (AR) with trypsin and pepsin were comparably investigated for deep revelations of conformational structures and activities of proteinases affected by food colourant. Various results indicated that one AR bound with one proteinase to form novel ground state complex under the binding forces of van der Waal interactions and hydrogen bonds. Intrinsic fluorescence of proteinases was quenched by AR via static fluorescence quenching mode. Conformational structures of proteinases were all changed obviously after their binding interactions with AR, resulting in their structure transformation to the β-sheet structure. AR bound with the allosteric site of proteinases to inhibit their activities via non-competitive manner. Finally, AR protected human serum albumin from the digestion of proteinases efficiently. These results revealed the exact binding mechanisms of food colourant AR with proteinases, which illuminated the possible biological risk of food colourant AR on human beings.