Key role of Fe(2+) in epithiospecifier protein activity

Area of Science:

• Plant biochemistry
• Nutritional science
• Enzymology

Background:

• Glucosinolate hydrolysis yields various products, with epithiospecifier proteins (ESPs) directing the outcome.
• Isothiocyanates, derived from glucosinolates, are crucial for human health due to their enzyme-inducing properties.
• The role of iron (Fe) in ESP activity is critical but not fully understood, with conflicting research findings.

Purpose of the Study:

• To investigate the precise role of iron species in regulating ESP activity.
• To analyze the impact of iron, chelators, and reducing agents on glucosinolate hydrolysis products.
• To examine how seed aging and early seedling development affect ESP activity and iron levels.

Main Methods:

• Analysis of ESP and myrosinase activities in four ESP-containing plant systems.
• Quantification of endogenous iron content.
• Assessment of glucosinolate degradation products following addition of iron species, chelators, and reducing agents.
• Testing of aged seeds and seedlings to evaluate developmental effects.

Main Results:

• Two distinct responses observed in ESP-containing plants, indicating varied Fe(2+) requirements for ESP activity.
• Ferric to ferrous iron reduction was identified as the driver of ESP activity changes during plant development.
• Oxidation of ferrous to ferric iron explained the loss of ESP activity during seed storage.
• Aged seeds yielded seedlings with reduced ESP activity and germination rates.

Conclusions:

• ESPs exhibit significant variability in their dependence on Fe(2+) for activity.
• Iron reduction is key for ESP activity during early plant development, while oxidation leads to loss of activity during seed storage.
• Modulating iron levels in ESP-containing plants offers a strategy to increase isothiocyanate production and associated health benefits.