The study of Zn2+ and Cu2+ effects on myrosinase activity and sulforaphane production in Lepidium draba

Myrosinase is a β-thioglucoside glucohydrolase enzyme which catalyzses the separation of glucose from glucosinolates and produces an unstable intermediate, aglycone. This intermediate will be rearranged and then converted to different compound such as thiocyanate, isothiocynate and nitrile, depending on the environmental conditions. Among them, isothiocyanates are more important compounds due to the pharmaceutical applications. Sulforaphane is the most isothioyanates which produces from glucosinolate glucoraphanin through myrosinase hydrolysis. In this study, in order to investigate the effects of Cu and Zn ions on myrosinase activity and rearrangement of aglycone fragment in Lepidium draba, glucose and sulforaphane content were measured respectively. The results showed that myrosinase activity significantly promoted at treatment with 8 µM ZnP2 in compared to the control and significantly reduced by the increase ZnP2 concentration in media. Elevated of the enzyme activity was seen at all Cu concentration which was more significant at 4 µM. On the other hand, sulforaphane content was reduced at presence of all concentrations of the both ions especially Zn ions. Overall, it deduced that the mentioned ions, especially Cu at low concentrations have stimulatory effects on myrosinase activity. These ions also affected rearrangement of the aglycone fragment particularly Zn which turned the rearranged pathway into other compound except isothiocyanates, therefore the sulforaphane content reduced at presence of these metals.