Glutamine as an Ammonia Donor in Catabolism of the Glucosinolate, Sinalbin, in Biosynthesis of 4‑Hydroxybenzylamine

Amines synthesized by plants may be considered a dietary source of bioactive compounds, which are of interest due to possible health promoting effects. Developing Sinapis alba sprouts are known to produce 4-hydroxybenzylamine, but the reaction mechanism has not yet been established. We propose here a suggested metabolic pathway for the formation of 4-hydroxybenzylamine in S. alba plants. The catabolic sequence starts with a reaction between l-glutamine (Gln) as ammonia donor and 4-hydroxybenzyl carbocation, the enzymatic catalyzed hydrolysis product from sinalbin (4-hydroxybenzyl­glucosinolate). The suggested reactions are compared with alternative plant metabolic reactions used in the biosynthesis of biogenic amines.