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BACKGROUND Proteins enzymatic digestion is a very complex process, during which some components are degraded, whereas others remain in an unchanged form. Moreover, enzymatic hydrolysis is one of the most popular methods used to reduce the allergenicity of food proteins. In the present study, the efficiency of enzymatic hydrolysis of lupin seed proteins was assessed by proteomic analysis as performed by two-dimensional gel electrophoresis (2- DE) coupled with mass spectrometry identification. Two digestion systems were used: oriented digestion carried out by trypsin and model in vitro digestion mimicking the conditions present in the gastrointestinal tract. RESULTS The comparisons of 2- DE maps of proteins isolated form different lupin seed species revealed that the differences in proteins expression were observed mainly in the central parts of gels (i.e. in the molecular weight range from 20 to 70 kDa, and the pH range 5-7). In total, 27 differentially expressed proteins spots were successfully identified by mass spectrometry analysis. An important reduction in the number of proteins spots on 2- DE maps was observed when trypsin and the in vitro digestion model were applied. The protein spot insensitive to digestion in both hydrolysis systems was identified as β-conglutin. CONCLUSIONS The results of the present study provide insight into the nature of the digestion process that may take place after lupin seed protein intake and highlight the important fact that some of the proteins are insensitive to digestive enzyme activity. Moreover, evaluation of digestion activity of trypsin towards lupin seed proteins may be used for the development of specific processes with respect to hypoallergenic food production. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Background: Basic 7S globulins, a group of proteins commonly found in legumes, undergo the intriguing phenomenon of release from the seeds into hot water. γ-Conglutin is a representative of this group of proteins found in lupin seeds. The physiological significance and the molecular mechanism of the selective release of γ-conglutin from lupin seeds remain unknown. Therefore, the presented study aimed to determine changes in the functionality of this protein in response to the high temperature occurring during lupin seed incubation., Results: It was confirmed that the main protein fraction released from the seeds during high-temperature incubation was γ-conglutin. The incubation condition favours the occurrence of this protein in a monomeric form, and the temperature used corresponds to its midpoint unfolding temperature. Subsequent analysis carried out on the γ-conglutin monomer revealed changes in its functionality after heat shock. The thermally treated protein shows a considerable increase in its interaction strength with flavonoids. Moreover, the inhibitory activity against glycoside hydrolases was enhanced when γ-conglutin monomer was exposed to specific temperatures., Conclusion: The results of the present study provide a potential explanation of the physiological relevance of γ-conglutin and shed new light on a possible mechanism of its activation upon specific heat treatment. This knowledge will help characterise homologous proteins, which are commonly found in other legumes and undergo a similar heat-induced secretion phenomenon. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)