Geranyl diphosphate biosynthesis

Gem, see Geminal, 705 Geminal (gem), 705 Genome, size of in humans. 1107 Gentamicin, structure of, 1002 Geraniol, biosynthesis of, 382 Geranyl diphosphate, biosynthesis of, 1077-1078... 

Propose a mechanistic pathway for the biosynthesis of cr-terpineol from geranyl diphosphate. 

The late cannabinoid pathway starts with the alkylation of ohvetolic acid (3.2 in Fig. 4) as polyketide by geranyl diphosphate (3.1) as the terpenoid unit. Terpenoids can be found in all organisms, and in plants two terpenoid pathways are known, the so called mevalonate (MEV) and non-mevalonate (DXP) pathway as described by Eisenrich, lichtenthaler and Rohdich [23,24,29,30]. The mevalonate pathway is located in the cytoplasm of the plant cells [30], whereas the DXP pathway as major pathway is located in the plastids of the plant cells [29] and delivers geranyl diphosphate as one important precursor in the biosynthesis. 

Figure 9.4 Monoterpene biosynthesis in peppermint oil gland secretory cells. The enzymes involved in this pathway are (1) 1-deoxy-D-xylulose 5-phosphate synthase, (2) 2-C-methyl-D-erythritol 4-phosphate reductoisomerase, (3) 2-C-methyl-D-erythritol 4-phosphate cytidyltransferase, (4) 4-(cytidine 5 -diphospho)-2-C-methyl-D-erythritol kinase, (5) 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase, (6) isopentenyl diphosphate isomerase, (7) geranyl diphosphate synthase, (8)...

Turner GW, Croteau R (2004) Organization of monoterpene biosynthesis in Mentha. Immunocytochemical localizations of geranyl diphosphate synthase, Umonene-6-hydroxylase, isopiperitenol dehydrogenase, and pulegone reductase. Plant Physiol 136 4215 227... 

The mechanism and stereospecificity of the enzyme catalyzed cyclization of geranyl diphosphate, 505 to 506 and other mono- and bicyclic unsaturated products, proceeds according to the established 605-609 mechanism (equation 296) involving a transient a-terpinyl carbonation intermediate 508 (produced from 507), which by the final proton elimination step yields 506. Recent tritium tracer and KIE610 study of this terminating proton transfer supplemented the biosynthesis of 506. 

Figure 6.10 De novo biosynthesis of isoprenoid pheromone components by bark and ambrosia beetles through the mevalonate biosynthetic pathway. The end products are hemiterpenoid and monoterpenoid pheromone products common throughout the Scolytidae and Platypodidae (Figure 6.9A). The biosynthesis is regulated by juvenile hormone III (JH III), which is a sesquiterpenoid product of the same pathway. The stereochemistry of JH III is indicated as described in Schooley and Baker (1985). Although insects do not biosynthesize sterols de novo, they do produce a variety of derivatives of isopentenyl diphosphate, geranyl diphosphate, and farnesyl diphosphate. Figure adapted from Seybold and Tittiger (2003).

Figure 6.15 Hypothetical alternative late stages of enantiospecific de novo biosynthesis of ipsenol and ipsdienol in male Ips paraconfusus and Ips pini. Biosynthesis may proceed from geranyl diphosphate to myrcene as catalyzed by a sex-specific monoterpene synthase. Terpene synthases (including a myrcene synthase) have been characterized from conifers (Bohlmann et al. 1997, 1998). Alternatively, biosynthesis may proceed from geranyl diphosphate to 5-hydroxygeranyl diphosphate (W. Francke, personal communication).

Young A., Tittiger C., Welch W. and Blomquist G. J. (2001) Monoterpenoid pheromone biosynthesis fishing for the elusive geranyl diphosphate synthase in bark beetles. Presented at Annu. Meet. Int. Soc. Chem. Ecol., 18th, Lake Tahoe. 

Figure 1 Schematic overview of the biosynthesis of the monoterpenoids, sesquiterpenoids, diterpenoids, and triterpenoids. Representatives of these classes with biological relevance are shown. Enzymatic steps are indicated in italics DMADP, dimethylallyl diphosphate CDP, geranyl diphosphate GGDP, geranylgeranyl diphosphate FDP, farnesyl diphosphate IDP, isopentenyl diphosphate.

---