Chorismate derived C6C1 compounds in plants

Abstract

The secondary metabolites are the products of interac tion of the producing organism with its environment and have a restricted occurrence. Many have economical importance as, e.g. drugs, antioxidants, flavors, fra grances, dyes, insecticides and pheromones (Verpoorte et al. 2002). Secondary metabolites can be classified according to their biosynthetic building blocks or their carbon skeleton. The C6C1 compounds are compounds having an aromatic six-carbon ring with one carbon attached. They are generally derived from the shikimate pathway (Dewick 2002). The shikimate pathway, restricted to microorganisms and plants, includes seven metabolic steps, starting with phosphoenolpyruvate and D-erythrose-4-phosphate, and ending with chorismate (an important metabolic branch point) (Fig. 1). All enzymes involved have been purified and the cDNAs characterized from some prokaryotes and eukaryotes (Herrmann and Weaver 1999). In plants, the pathway is localized in plastids.Gallic acid and protocatechuic acid (3,4-dihydroxybenzoic acid) are C6C1 compounds that can derive from either shikimate pathway (by dehydration and dehydrogenation of 3 dehydroshikimic acid) or phenylalanine pathway (via 3,4,5-trihydroxycinnamic acid) (Torssell 1997; Ossipov et al. 2003). Gallic acid can also derive from orsellinic acid via the polyketide pathway by decarboxylation and oxidation (Torssell 1997). This review will focus on chorismate-derived C6C1 compounds in plants, includ