Terpenoids tyrosine

L-tyrosine Tyrosine-derived alkaloids Indole alkaloids Quinoline alkaloids /3-carboline alkaloids Pyrroloindole alkaloids Ergot alkaloids Iboga alkaloids Corynanthe alkaloids Aspidosperma alkaloids Protoalkaloids Terpenoid indole alkaloids True alkaloids... 

In contrast to the rutelines, the melolonthine scarabs generally use terpenoid-and amino acid-derived pheromones (reviewed in Leal, 1999). For example, the female large black chafer, Holotrichia parallela Motschulsky, produces methyl (2.S, 3. Sj - 2 - am ino-3-methy lpcn tanoatc (L-isoleucine methyl ester) as an amino acid-derived sex pheromone (Leal et al., 1992 Leal, 1997). There is no direct evidence that the chafer beetles or any other Coleoptera use the shikimic acid pathway for de novo pheromone biosynthesis, but some scarabs and scolytids (see section 6.6.4.2) may convert amino acids such as tyrosine, phenylalanine, or tryptophan to aromatic pheromone components (Leal, 1997,1999). In another melolonthine species, the female grass grab beetle, Costelytra zealandica (White), the phenol sex pheromone is produced by symbiotic bacteria (Henzell and Lowe, 1970 Hoyt et al. 1971). 

Alkaloids thus represent one of the largest groups of natural products, with over 10,000 known compounds at present, and they display an enormous variety of structures, which is due to the fact that several different precursors find their way into alkaloid skeletons, such as ornithine, lysine, phenylalanine, tyrosine, and tryptophan (38-40). In addition, part of the alkaloid molecule can be derived from other pathways, such as the terpenoid pathway, or from carbohydrates (38-40). Whereas the structure elucidation of alkaloids and the exploration of alkaloid biosynthetic pathways have always commanded much attention, there are relatively few experimental data on the ecological function of alkaloids. This is the more surprising since alkaloids are known for their toxic and pharmacological properties and many are potent pharmaceuticals. 

The majority of alkaloids have been found to be derived from amino acids, such as tyrosine, phenylalanine, anthranilic acid, tryptophan/tryptamine, ornithine/arginine, lysine, histidine and nicotinic acid (Fig. 2.1). However, alkaloids maybe derived from other precursors such as purines in case of caffeine, terpenoids, which become aminated after the main skeleton has been synthesized i.e. aconitine or the steroidal alkaloids, are found in the Solanaceae and Liliaceae. Alkaloids may also be formed from acetate-derived polyketides, where the amino nitrogen is introduced as in the hemlock alkaloid, coniine. 

Figure 14.11 illustrates the syntheses of phenylalanine, tyrosine, and tryptophan from chorismate. (Chorismate is also a precursor in the synthesis of the aromatic rings in the mixed terpenoids, e.g., the tocopherols, the ubiquinones, and plastoquinone.)... 

It is usual to classify alkaloids (basic nitrogenous metabolites) according to the amino acids (or their derivatives) from which they arise. Thus, the most important classes are derived from the amino acids ornithine, lysine, phenylalanine, tyrosine and tryptophan, and the skeletons of these amino acids are retained largely intact in the alkaloids derived from them. However, this type of classification is often criticized because it fails to include those alkaloids that are derived from a mixed biogenetic pathway (e.g. polyketide or terpenoid) with incorporation of a nitrogen atom, ultimately from ammonia. The alkaloids that are the subject of this review are excellent examples of such compounds and they are often known as pseudoalkaloids. 

The indole moiety of the terpenoid indole alkaloids originates from tryptophan, an aromatic amino acid, which is derived from chorismate via anthranilate. Chorismate is a major branching point in plant primary and secondary metabolism. Here the shikimate pathway (Fig. 6) branches into different pathways (Fig. 7), among others leading to the aromatic amino acids tyrosine, phenylalanine, and tryptophan. 

Ubiquinones (UQ), often called coenzyme Qio, are electron carriers in oxidative phosphorylation and photosynthesis, respectively. Ubiquinones consist of quinoid nucleus (derived from the shikimate pathway), 4-hydroxybenzoate (derived from chorismate or tyrosine), and terpenoid moiety. Zeatin, a phytohormone, is a member of the cytokinin family involved in various processes of growth and development in plants. Most cytokinins are adenine-type, where the hydrogen of amino group at Ce position of adenine is replaced with an isoprenoid. 

Ipecac alkaloids are derived from the amino acid tyrosine and the monoterpene secologanin and are therefore termed terpenoid-isoquinoline alkaloids. They occur in the eudicot families Alangiaceae and Rubiaceae. Two species, Psychotria ipecacuanha (Rubiaceae) and Alangium lamarckii (Alangiaceae), have been investigated in detail with respect to their metabolites and biosynthesis of their alkaloids (Fujii and Ohba, 1998). Roots and rhizomes of P. ipecacuanha are the source of cephaeline and emetine (Fig. 9), two compounds with emetic, expectorant, and amebicidal properties. 

Transcripts that encode all of the enzymes involved in the biosynthesis of vitamin E are elucidated in Table 18.2. The identified enzymes used to reconstruct the pathway of vitamin E bios5mthesis are presented in Fig. 18.3. The vitamin E biosynthetic pathway in D. tertiolecta is similar to that of the plant AraUdopsis thaliana, and the cyanobacterium Synecho-cystis sp. D. tertiolecta utilizes the metabolism of the aromatic amino acid tyrosine for the s5mthesis of the polar head group, whereas the unsaturated tail is derived from phytyl-pyrophosphate (PPP), which is a metabolite of terpenoid backbone biosynthesis (DellaPenna and Pogson, 2006). The committed step in the synthesis of the head group is catalyzed by the enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD, EC 1.13.11.27), which converts... 

Terpene hydrocarbons Terpenoids L-leucine L-tryptophan L-tyrosine L-phenylalanine Magnesium sulfate Denatorium benzoate (Bitrex)... 

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