Terpenoids biosynthetic pathway

Much attention has been paid to the last step of the formation of monoter-penes and sesquiterpenes, which is catalysed by terpenoid synthases. Over 30 complementary DNAs (cDNAs) encoding plant terpenoid synthases involved in the primary and secondary metabolism have been cloned, characterised, and the proteins heterologously expressed [6]. However, because geranyl diphosphate and farnesyl diphosphate are not readily available substrates, their biotransformation by terpenoid synthases is not economically viable. As a result, considerable effort has been put into engineering the total plant terpenoid biosynthetic pathway in recombinant microorganisms. 

Extracts of Pterogorgia anceps contain a fraction enriched in ancepsenolide metabolites of the polyketide class, one of which (134) is individually deterrent in shipboard assays with T. bifasciatum 0 This last study illustrates that chemical defense mechanisms in gorgonians do not solely rely on the terpenoid biosynthetic pathway. 

Concerning the chemical sjmthesis of this type of compounds, this appears non viable in economic terms and, taking into account that secondary metabolites are often produced in very low amounts in the mother plants, the genetic modification of the terpenoid biosynthetic pathway would be an attractive alternative to obtain a continuous source of these valuable metabolites because it offers the possibility of manipulating cells, tissues or even complete organisms in order to obtain a continuous and accurate source of these secondary metabolites. 

The results from kinetic studies of MVK in Methanococcus jannaschii, showed that the Arg 196 is an essential residue for the function of this enzyme and the Lys 272-Glu 14 plays an important role in maintaining the active site microenvironment that is essential for the catalytic activity of this enzyme [285]. These results suggest that MVK has a regulating role in the terpenoid biosynthetic pathway, as well as in several growth and development processes in plants. 

In D. punctata, JH III is biosynthesized in retrocerebral endocrine organs, the corpora allata (CA) [45]. The sesquiterpenoid skeleton of this compound is formed through the terpenoid biosynthetic pathway from acetyl-CoA. The early steps of this pathway involve the sequential condensation of three acetyl-CoA molecules (3 x 2C) to form the biosynthetic intermediate mevalonate (MVA, 6C). 3-Hydroxy-3-methylglutaryl CoA reductase, which catalyzes the formation of MVA, is thought to be the rate-limiting enzyme in this pathway [59], although the... 

The subcellular compartmentation of terpenoid metabolism is a matter of controversy. Chloroplasts seem to contain the entire terpenoid biosynthetic pathway and appear to be autonomous in regard to terpene biosynthesis. Carotenoids and the side chains of chlorophyll are synthesized in the chloroplasts. Sterols are synthesized in the cytoplasm (Gershenzon and Croteau, 1990). 

K.L.J. (2010) Combining metabolic and protein engineering of a terpenoid biosynthetic pathway for overproduction and selectivity control. Proc. Nad. Acad. Sci. US.A., 107, 13654-13659. 

Ajikumar PK, Xiao W-H, Tyo KEJ, Wang Y, Simeon F, Leonard E, Mucha O, Phon TH, Pfeifer B, Stephanopoulos G (2010) Isoprenoid pathway optimization for taxol precursor overproduction m Escherichia coli. Science 330(6000) 70-74. doi 10.1126/science.l 191652 Albrecht M, Misawa N, Sandmann G (1999) Metabolic engineering of the terpenoid biosynthetic pathway of Escherichia coli for production of the carotenoids p-carotene and zeaxanthin. Biotechnol Lett 21(9) 791-795... 

The production of copious trichome resin products raises the question of whether or not these resins are adaptive. Various proposals have been advanced regarding the defensive role of such compounds and the link between their structural variability and the coevolutionary process. However, there is little evidence linking these compound s biological function to the fine detail of their structural variability. The extent to which the observed chemical variability is an expression of past selection for specific novel chemical deterrents rather than the product of near-random activation of alternative terpenoid biosynthetic pathways is not known. Thus, in looking at the diterpene variability within the Compositae, care should be exercised in automatically associating a discrete adaptive function with each novel chemistry. 

Without proposing an entire biosynthetic pathway, draw the appropriate precursor, either geranyl diphosphate or farnesvl diphosphate, in a conformation that shows a likeness to each of the following terpenoids ... 

Termination step (radical), 141 Terpenoid. 202-204, 1070-1078 biosynthesis of, 1071-1078 classification of, 1071 DXP biosynthetic pathway of, 1071... 

Many phytotoxic compounds produced by higher plants are phenolic compounds. Several of these have been implicated in allelopathy. Based on the biosynthetic pathway from which they are derived, phenolic compounds produced by higher plants fall into two general categories 1) terpenoid phenolic compounds derived from five... 

Weathers PJ, Elkholy S, Wobbe KK. (2006) Artemisinin the biosynthetic pathway and its regnlation in Artemisia annua, a terpenoid-rich species. In Vitro Cell Developmental Biol — Plant 42 309-317. 

The diverse, widespread and exceedingly numerous class of natural products that are derived from a common biosynthetic pathway based on mevalonate as parent, are synonymously named terpenoids, terpenes or isoprenoids, with the important subgroup of steroids, sometimes singled out as a class in its own right. Monoterpenes, sesquiterpenes, diterpenes and triterpenes are ubiquitous in terrestrial organisms and play an essential role in life, as we know it. Although the study of terrestrial terpenes dates back to the last century, marine terpenes were not discovered until 1955. 

In relation with resistance of weeds to herbicides, Duke et al. (2000) mentioned that new mechanisms of action for herbicides are highly desirable to fight evolution of resistance in weeds, to create or exploit unique market niches, and to cope with new regulatory legislation. Comparison of the known molecular target sites of synthetic herbicides and natural phytotoxins reveals that there is little redundancy. Comparatively little effort has been expended on determination of the sites of action of phytotoxins from natural sources, suggesting that intensive study of these molecules will reveal many more novel mechanisms of action. These authors gave some examples of natural products that inhibit unexploited steps in the amino acid, nucleic acid, and other biosynthetic pathways AAL-toxin, hydantocidin, and various plant-derived terpenoids. 

Regulation of the Terpenoid Indole Alkaloid Biosynthetic Pathway 111... 

Figure 7.3 Biosynthetic pathway for terpenoid indole alkaloids showing the location of enzymes for which the corresponding cDNAs have been isolated.

Aroma-active molecules of natural origin are mainly formed via well-known biosynthetic pathways.17,27-29 The major class is the terpenoids followed by phenylpropanoid compounds (see Chapters 1.15, 1.16, and 1.24). Enzymatic and biosynthetic transformation and cleavage of fatty acid is another important source of aroma-active compounds (see Chapter 8.07). Transformation of amino acids and carbohydrates by fermentation is also... 

This brief survey of natural products derived from the 3-deoxy-D-oro6iTk>-heptulosonic acid 7-phosphate pathway illustrates the economy of fimda-mental biosynthetic pathways. The relative economy and simplicity of the biological degradative and energy-yielding reactions is paralleled in the biosynthetic reactions. For example, 3-deoxy-D-oroW o-heptulosonic acid 7-phosphate is a precursor of a host of aromatic products mevalonic acid is the progenitor of the terpenoids and steroids, and 5-aminolevulinic acid of the porphyrins. 

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 biosynthetic pathway to terpenoids (Fig. 5.2) is conveniently treated as comprising four stages, the first of which involves the formation of IPP,... 

The biosynthetic pathway for ajmaline in R. serpentina is one of the best-characterized terpenoid indole alkaloid pathways. Much of this progress has been detailed in a recent extensive review (78). Like all other terpenoid indole alkaloids, ajmaline, an antiarrhythmic drug with potent sodium channel-blocking properties (79), is derived from deglycosylated strictosidine (Fig. 2c). 

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