Pathways to glucosinolates

Review TRENDS in Plant Science Vol.11 No.2 February 2006hydrolysis of the glucosidic bond. Myrosinases are specificThe glucosinolate-defining core structure (the glucone) is derived from select protein amino acids and comprises a b-thioglucosyl residue attached to the original a-carbon to form a sulfated ketoxime (Figure 1). Extensive glucosino-late side-chain modification and amino acid elongation are together responsible for the chemical diversity of the more than 120 reported structures [7]. These hydrophilic, stable compounds are normally sequestered in vacuoles of most plant tissues [9]. Loss of cellular integrity initiates glucosinolate breakdown by myrosinase-catalyzed Biosynthesis of glucosinolates proceeds in three stages: (i) side-chain elongation of amino acids, (ii) development of the core structure, and (iii) secondary side-chain modifi-cations (Figure 2). Gene identification in Arabidopsis followed by in vitro and in vivo characterization of the gene products have confirmed the tripartite biosynthetic concept derived from early biochemical studies [8,20–22]. The core pathway, common to all glucosinolates, has received the most study in Arabidopsis, and relatively few gaps in our understanding remain. Side-chain elongationthaliana [7,8]. importance as well as the reference plant ArabidopsisGlucosinolate meta contro