Animals terpenoid pathway

The terpenoid precursor isopentenyl diphosphate, formerly called isopentenyl pyrophosphate and abbreviated IPP, is biosynthesized by two different pathways depending on the organism and the structure of the final product. In animals and higher plants, sesquiterpenoids and triterpenoids arise primarily from the mevalonate pathway, whereas monoterpenoids, diterpenoids, and tetraterpenoids are biosynthesized by the 1-deoxyxylulose 5-phosphate (DXP) pathway. In bacteria,... 

It is difficult to reconcile the unique chemical structure of tetrodotoxin with that of an animal product. Its structure is not related to that of other animal products by any readily recognized biosynthetic scheme. It is not a terpenoid, not obviously formed from amino acid or carbohydrate units, and apparently not constructed from acetate or propionate units. Nor does it resemble any of the various plant alkaloid patterns. It thus appears to be a very unlikely animal product to result from known biogenetic pathways. In this connection the metabolic incorporation of radioactive precursors using torosa and ]C. granulosa salamanders was studied by Shimizu et al. (47). They observed significant isotopic incorporation into amino acids and steroid metabolites, but they found no such incorporation associated with tetrodotoxin. 

This would favour hypothesis II in Fig. 7.15. Even animals share some of the proteins (TDC, ODC, TyrDC, STS and CR). These observations indicate that the proteins very likely evolved in prokaryotes and were transferred into eucaryotes via either protobacteria (Fig. 7.18) or cyanobacteria, the progenitors of mitochondria or chloroplasts, respectively. A number of SM (e.g. many terpenoids, QAs, the piperidine alkaloid coniine) are produced completely or partly in chloroplasts and/or mitochondria (see Chapter 1). The corresponding genes are mostly nuclear today. It is tempting to speculate that these localizations are indirect indicators of a former bacterial origin of the corresponding pathways. The introduction of bacterial genomes into eukaryotes was... 

The importance of terpenoids to life is highlighted by the fact that two separate pathways have been found to produce the terpenoid precursor C5 units isopentenyl diphosphate (IDP) and dimethylaUyl diphosphate (DMADP). The mevalonic acid (MVA) pathway is functional in archae, animals and fungi, 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway is found in green algae, and terpenoids are produced by both pathways in bacteria and plants [2]. In plants the MVA pathway is active in the cytosol and it provides C5 units for sesquiterpene, triterpene and polyterpene biosynthesis whereas the MEP pathway occurs in plastids and produces C5 units for isoprene, monoterpenes, diterpenes and carotenoids [1]. Recent reports have indicated metabolic crosstalk between biosynthesis pathways and e.g., the homoterpene DMNT may originate from both pathways. 

The above description clearly demonstrates that phenolics and terpenoids modulate multiple signal transduction pathways and interact with multifactorial molecular targets, including inflammatory molecules, growth factors, enzymes, and genes regulating cell proliferation and apoptosis. This collection of information verifies the efficacy of phenolic and terpeniod use in the prevention and curing of various conditions. In vitro, in vivo, and animal studies have all confirmed the efficacy of plant-isolated compounds, such as phenolics and terpenoids, in... 

Animals appears to lack DXP pathway completely, thus formation of terpenes is exclusively produced by mevalonate pathway. It has to be pointed out that inhibitors of mevalonate pathway enzyme HMG-CoA reductase, like statins, do not affect the production of terpenoids by DXP pathway due to the absence of the particular enzyme in this metabolic pathway. On the other hand, it is possible to inhibit terpenoid production without affecting steroid formation by selectively inhibit DXP pathway in plants (e.g., fosmidomycin antibiotic) [5b, 28]. 

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