Characterisation of different digestion susceptibility of lupin seed globulins

This study describes in vitro digestion of lupin seed globulins by pancreatin, trypsin and chymotrypsin. Lupin seed globulins turned out to be almost totally susceptible to chymotrypsin digestion. When panceratin or trypsin were used for digestion of lupin seed globulins, γ-conglutin appeared to be resistant to proteolysis. Different fluorescence spectroscopic methods such as fluorescence anisotropy, fluorescence lifetimes and fluorescence quenching measurements were used for detailed characterisation of this phenomenon. A potential reason for γ-conglutin insensitivity to digestion may be related to the fact that lysine, as well as arginine, are positively charged at cell physiological pH. Simultaneously, flavonoids at this pH are partially ionised, which may lead to the occurrence of ionic interactions between these molecules at pH 7.5. The confirmation of this explanation may be the fact that γ-conglutin and vitexin form a static complex, which was observed using fluorescence quenching measurements.