Dehydroquinate pathway production

Figure 1. Schematic outline of various products and associated enzymes from the shikimate and phenolic pathways in plants (and some microorganisms). Enzymes (1) 3-deoxy-2-oxo-D-arabino-heptulosate-7-phosphate synthase (2) 5-dehydroquinate synthase (3) shikimate dehydrogenase (4) shikimate kinase (5) 5-enol-pyruvylshikimate-3-phosphate synthase (6) chorismate synthase (7) chorismate mutase (8) prephenate dehydrogenase (9) tyrosine aminotransferase (10) prephenate dehydratase (11) phenylalanine aminotransferase (12) anthranilate synthase (13) tryptophan synthase (14) phenylalanine ammonia-lyase (15) tyrosine ammonia-lyase and (16) polyphenol oxidase. (From ACS Symposium Series No. 181, 1982) (62).

Quinic acid, a compound accumulated by many green plants, can be formed by reduction of 3-dehy-droquinate (Eq. 25-2) in both plants and bacteria. Quinic acid can be converted into useful industrial products such as benzoquinone and hydroquinone, and its production by bacteria provides a convenient route to these compounds.168 In the main shikimate pathway 3-dehydroquinate is dehydrated to 3-dehydroshikimate (Eq. 25-3). The latter can be dehydrated... 

This product is dehydroquinic acid and is an intermediate on the way to shikimic acid. It is also in equilibrium with quinic acid, which is not an intermediate on the pathway but which appears in some natural products like the coffee ester caffeyl quinic acid. 

We quantified DAHP production by various E. coli aroB strains in order to understand the effect of certain parameters on direction of carbon flow into the common pathway (31,32). A mutation in the gene (aroB) encoding 3-dehydroquinate (DHQ) synthase leaves E. coli aroB strains incapable of converting... 

The shikimic acid pathway begins with phosphoenolpyruvate which is obtained from glycolysis, and D-erythrose-4-phosphate, which comes from the pentose phosphate cycle. The two are linked to form an intermediate with 7 C atoms which cyclizes to 5-dehydroquinic acid. The latter exists in equilibrium with quinic acid. The pathway proceeds via 5-dehydroshikimic acid and shikimic acid to 5-phosphoshikimic acid. An additional phosphoenolpyruvate unit is now attached to the last-mentioned compound. The product of this reaction is converted, in several steps, to chorismic acid. 

Individual common pathway enzymes become impediments to increased carbon flow due to their inability to convert substrate into product at a rate sufficiently rapid to avoid cytoplasmic accumulation and subsequent export of the substrate into the culture medium." 3-Dehydroquinate synthase and shikimate dehydrogenase are both impediments to increased carbon flow that result, respectively, in accumu-... 

Adachi O, Tanasupawat S, Yoshihara N, Toyama H, Matsushita K (2003a) 3-Dehydroquinate production by oxidative fermentation and further conversion of 3-dehydroquinate to the intermediates in the shikimate pathway. Biosci Biotechnol Biochem 67(10) 2124—2131... 

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