Secondary metabolites auxins

Aromatic Amino Acid Biosynthesis. The shikimate pathway is the biosynthetic route to the aromatic amino acids tryptophan, tyrosine and phenylalanine as well as a large number of secondary metabolites such as flavonoids, anthocyanins, auxins and alkaloids. One enzyme in this pathway is 5-enolpyruvyl shikimate-3-phosphate synthase (EPSP synthase) (Figure 2.9). 

Cell suspension cultures are established from callus after plant cell dedifferentiation using growth regulators, such as auxins. The dedifferentiation proeess it is frequently accompanied by the loss of the ability to produce secondary metabolites. In addition, undifferentiated cells grows slowly (doubling times of 4-6 days) and it is frequently observed instability and genetic heterogeneity [48]. 

In order to improve yields and productivities of secondary metabolites in plant cell culture s it is essential the selection of the most elEcient plant growth regulators (auxins, cytokinins, gibberellic acid and abscicic acid) and the relationship between diem [74, 75]. 

Plant cell culture medium includes inorganic compounds and phytohormones. Changing the medium components (concentration, proportion, and form) is a very powerful way of enhancing the culture efficiency of plant cell cultures. Unsuitable conditions often reduce the efficiency. For example, high auxin levels can stimulate cell growth, but can often negatively influence secondary metabolite production. ... 

Secondary metabolites, produced by pathways derived from primary metabolic routes, are numerous and widespread, especially in higher plants. More than 20,000 were known in 1985 (Hartmann, 1985), and at least 1000 additional compounds, are described each year. In practice, the difference between the primary and secondary metabolites is fuzzy. Plant hormones such as gibberellic acid, indoleace-tic acid (auxin), ethylene, kinetin, and abscisic acid, as well as compounds involved in plant cell wall structure such as cinnamic acid and its polymeric derivative, lignin, are intermediate between primary and secondary metabolism (Birch, 1973). In some instances, compounds normally considered primary metabolites may accumulate in large amounts and behave in a manner usually associated with secondary metabolites. Entities such as shikimic acid and squalene, which initially were considered secondary metabolites, were subsequently shown to be important intermediates in the formation of primary metabolites (phenylalanine, tyrosine and tryptophan, and steroids, respectively). 

The metabolic pathway responsible for biosynthesis of aromatic amino acids and for vitamin-like derivatives such as folic acid and ubiquinones is a major enzyme network in nature. In higher plants this pathway plays an even larger role since it is the source of precursors for numerous phenylpropanoid compounds, lignins, auxins, tannins, cyano-genic glycosides and an enormous variety of other secondary metabolites. Such secondary metabolites may originate from the amino acid end products or from intermediates in the pathway (Fig. 1). The aromatic pathway interfaces with carbohydrate metabolism at the reaction catalyzed by 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthase, the condensation of erythrose-4-phosphate and PEP to form... 

The species Rhodymenia palmata is consumed imder the name dulse because it is rich in protein (about 40% of dry weight) and vitamins however, apart from the oxy-lipins mentioned earlier, there are very few publications on the secondary metabolites of Rhodymeniales. Among these, the identification of 3-formylindole in the species Botryodadia leptopoda is noteworthy because this derivative could come from /5-indole acetic add (lAA, auxin), an important plant growth hormone (Bano et al., 1986). More recently, p-sulfo-oxyphenylpyruvic add has been identified in Ceratodictyon spongiosum harvested in the Philippines. This acid, which exists mainly in the enolic form, is isolated mixed with p-hydroxyphenylpyruvic add (Bugni et al, 2002). 

Biogenic amines are a group of aliphatic, aromatic or heterocychc bases derived from amino acids, which exhibit a variety of biological effects, as they perform different functions in animal and plant tissues. Some biogenic amines are building materials for the biosynthesis of phytohormones of the auxin group, plant protoalkaloids (such as hordenine and gramine), true alkaloids and other secondary plant metabolites. In animal tissues they have the function of tissue hormones (e.g. histamine) and are precursors of adrenal hormones (catecholamines). 

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