5-Dehydroshikimic acid

Some biochemical processes involve alcohol dehydration as a key step An example IS the conversion of a compound called 3 dehydroquimc acid to 3 dehydroshikimic acid... 

FIGURE 3.2 The common aromatic pathway to chorismate in Escherichia coli K12, where 5 is phosphoe-nolpyruvate, 6 is erythrose 4-phosphate, 7 is 3-deoxy-D-arabinoheptulose 7-phosphate, 8 is 3-dehydroquinic acid, 9 is 3-dehydroshikimic acid, 10 is shikimic acid, 11 is shikimic acid 3-phosphate, and 12 is 5-enolpyru-vylshikimic acid 3-phosphate. 

Intermediates in the biosynthetic route are 3-dehydroshikimic acid, protocate-chuic acid and catechol (Scheme 7.16). Optimization of microbial ds,ds-muconic acid synthesis required the expression of three enzymes not typically found in Escherichia coli [42cj. E. coli WNl/pWN2.248 was developed that synthesized 36.8 g of ds,ds-muconic acid in a 22% (mol/mol) yield from glucose after 48 h of culturing under fed-batch fermentor conditions. Optimization of the carbon flow directed into ds,ds-muconic acid biosynthesis and manipulation of enzyme activities were aimed at avoiding accumulation of biosynthetic intermediates. 

Biosynthesis There are at least three pathways to G. dehydrogenation of 3-dehydroshikimic acid, side-chain degradation of hydroxylat hydrocinnamic acid, and hydroxylation of oxidized benzoic acids. 

Activity For Q. esters from artichokes with cholagogic activity, see cynarin(e). Q. is used in treatment of gout. Q. is formed by reduction of 3-dehydroshikimic acid in the shikimate pathway. 

Biosynthesis 3-Deoxy-D-araW o-2-heptulosonic acid 7-phosphate - 3-dehydroquinic acid (see quinic acid) - 3-dehydroshikimic acid - shikimic acid. 

Because of the lack of shikimic acid dehydrogenase, 3-dehydroshikimic acid accumulates. Catechol-0-methyltransferase is not very selective. Apart from methylation in the meta-position, the para-hydroxy group is also methylated to an extent of ca. 20 mole%. The addition of methionine increases significantly the vanillic acid content in the product mixture. 

Dehydroshikimic Acid A Building Block for Chemical Synthesis from Renewable Feedstocks... 

The linking molecules for both pathw s are 3-dehydroquinic acid and 3-dehydroshikimic acid. 3-dehydro-quinic acid can be formed in a one-step reaction catalysed by quinate-dehydrogenase from quinic acid, an abundant plant metabolite (Figure 2). 

Figure 2. The biosynthesis of 3-dehydroquinic acid and 3-dehydroshikimic acid from quinic acid (1... quinate-dehydrogenase 2... dehydrogenase).

Dehydoquinic acid is also synthesized in a sequence of enzymatically catalysed reactions from phosphoenolpyruvate and D-erythrose-4-phosphate which are both activated intermediates from the carbohydrate metabolism. As an unusual intermediate 3-dehydro-D-arabo-heptalose-7-phosphate (DAHP), a sugar containing 7 carbon atoms, is formed. After enzymatic condensation by DAHP-synthase followed by a dephosphorylation step, 3-dehydro-quinic acid is obtained and further transformed to 3-dehydroshikimic acid as shown above. 

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