In vitro enzymatic digestion of benzyl- and phenylisothiocyanate-derivatized food proteins

The interactions of different isothiocyanates (ITCs, benzyl- and phenyl-ITC) with selected;food proteins such as egg white proteins, myoglobin, and legumin have been investigated. The first aspect summarizes the changes in physicochemical properties of the derivatized proteins such as a decrease in solubility and in the amount of free E-amino groups coupled with an increase in the hydrophobicity. In,addition, the isoelectric points were shifted to lower pH values, demonstrated for legumin by isoelectric focusing of legumin. The main feature of this paper represents the proteolytic degradation (tryptic, chymotryptic, and peptic) of ITC-derivatized proteins (egg white proteins, myoglobin, and legumin), which leads to different degrees of digestion of the derivatives. The enzymatic progress has been monitored by RP-HPLC and SDS-PAGE. Proteolytic digestion was inhibited by ITC-derivatization (trypsin more inhibited than chymotrypsin = pepsin), due to the presence of derivatized lysine side chains that proved difficult to split.