Deoxyxylulose phosphate pathway

Rodriguez-Concepcion, M. and Boronat, A., Elncidation of the methylerythritol phosphate pathway for isoprenoid biosynthesis in hacteria and plastids a metabolic milestone achieved throngh genomics. Plant Physiol. 130, 1079, 2002. Rodriguez-Concepcion, M., Early steps in isoprenoid biosynthesis multilevel regulation of the supply of common precursors in plant cells, Phytochem. Rev. 5, 1, 2006. Eisenreich, W., Rohdich, F., and Bacher, A., Deoxyxylulose phosphate pathway to terpenoids, Trends Plant Sci. 6, 78, 2001. 

Rohdich, F., Zepeck, F., Adam, P. et al. (2003) The deoxyxylulose phosphate pathway of isoprenoid biosynthesis studies on the mechanisms of the reactions catalyzed by IspG and IspH protein. Proceedings of the National Academy of Sciences of the United States of America, 100, 1586-1591. 

EISENREICH, W., ROHDICH, F., BACHER, A., Deoxyxylulose phosphate pathway to terpenoids, Trends Plant Sci., 2001,6, 78-84. 

Terpenes, biogenetically, arise from two simple five-carbon moieties. Isoprenyl-diphosphate (IPP) and dimethylallyldiphosphate (DMAPP) serve as universal precursors for the biosynthesis of terpenes. They are biosynthesised from three acetylcoenzyme A moieties through mevalonic acid (MVA) via the so-called mevalonate pathway. About 10 years ago, the existence of a second pathway leading to IPP and DMAPP was discovered involving l-deoxy-D-xylulose-5-phos-phate (DXP) and 2C-methyl-D-erythritol-4-phosphate (MEP). This so-called non-mevalonate or deoxyxylulose phosphate pathway starts off with the condensation of glyceraldehyde phosphate and pyruvate affording DXP. Through a series of reactions as shown in Fig. 4.1, IPP and DMAPP are formed, respectively [3,7, 42, 43]. 

S ATP + 4-(cytidine 5 -diphospho)-2-C-methyl-D-erythritol <1> (<1> involved in terpenoid biosynthesis via deoxyxylulose phosphate pathway... 

In the 1970s the biosynthesis of cannabinoids was investigated with radiolabeling experiments. 14C-labeled mevalonate and malonate were shown to be incorporated into tetrahydrocannabinolic acid and cannabichromenic acid at very low rates (< 0.02%). Until 1990 the precursors of all terpenoids, isopentenyl diphosphate and dimethyl-allyl diphosphate were believed to be biosynthesized via the mevalonate pathway. Subsequent studies, however, proved that many plant terpenoids are biosynthesized via the recently discovered deoxyxylulose phosphate pathway (Eisenreich et al., 1998 Rohmer, 1999). It was shown that the Cio-terpenoid moiety of cannabinoids is biosynthesized entirely or predominantly (>98%) via this pathway (Fellermeister et al., 2001). The phenolic moiety is generated by a polyketide-type reaction sequence. 

For convenience, the major oils listed are divided into two groups. Those which contain principally chemicals which are aromatic in nature and which are derived by the shikimate pathway are given in Table 4.1 below. Those oils which are composed predominantly of terpenoid compounds are listed in Table 5.1 on page 177, since they are derived via the deoxyxylulose phosphate pathway. It must be appreciated that many oils may contain aromatic and terpenoid components, but usually one group predominates. The oil yields, and the exact composition of any sample of oil will be variable, depending on the particular plant material used in its preparation. The quality of an oil and its commercial value is dependent on the proportion of the various components. 

---