The myrosinase-glucosinolate interaction mechanism studied using some synthetic competitive inhibitors

Using synthetic deoxy-glucotropaeolins (6d-GTL, 4d-GTL, 3d-GTL, 2d-GTL) as substrates, myrosinase activity was studied in comparison to that determined on native glucotropaeolin (GTL) isolated from ripe Lepidium sativum seeds. When the deoxy substrates were used, in addition to an overall strong reaction rate decline, a significant decrease in the reaction rate was observed in going from 6d- to 2d-GTL. This finding allows us to propose a mechanism of catalysis which appears to be similar in many respects to that established for beta-glucosidases. Finally, 2d-GTL was shown to be the first strong competitive inhibitor of myrosinase ever reported.