3-deoxy-D-arabino-heptulosonate

Glyphosate also inhibits the activity of a form of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (13), however, this inhibition is relatively weak. Effects of glyphosate on the enzymes of aromatic amino acid synthesis have been described in more detail in recent reviews (14-17). 

Ran, N.Q. and Frost, J. W. (2007) Directed evolution of 2-keto-3-deoxy-6-phosphogalactonate aldolase to replace 3-deoxy-D-arabino-heptulosonic acid 7-phosphate synthase. Journal of the American Chemical Society, 129, 6130-6139. 

Figure 1. Hypothetical mechanism for shuttling of intermediates of the common aromatic pathway between plastidic and cytosolic compartments. Enzymes denoted with an asterisk (DAHP synthase-Co, chorismate mutase-2, and cytosolic anthranilate synthase) have been demonstrated to be isozymes located in the cytosol. DAHP molecules from the cytosol are shown to be shuttled into the plastid compartment in exchange for EPSP molecules synthesized within the plastid. Abbreviations C3, phosphoenolpyruvate C4, erythrose 4-P DAHP, 3-deoxy-D-arabino-heptulosonate 7-phosphate EPSP, 5-enolpyruvylshikimate 3-phosphate CHA, chorismate ANT, anthranilate TRP, L-tryptophan PPA, prephenate AGN, L-arogenate TYR, L-tyrosine and PHE, L-phenylalanine.

Figure 4. Reactions catalyzed by the broad-specificity DAHP synthase-Co of higher plant cytosol. Condensation of PEP and erythrose 4-P (top) yields 3-deoxy-D-arabino-heptulosonate 7-P (DAHP), whereas condensation of PEP and D-glyceraldehyde 3-P (G-3-P) yields 2-keto-3-deoxy-D-threo-hexulosonate 6-P (DTHP).

Accordingly, a strain of E. coli was first engineered to produce elevated levels of DHQ by increasing the levels of certain key enzymes transketolase, 3-deoxy-D-arabino-heptulosonic acid 7-phospate (DAHP) synthase, and DHQ synthase. Also, the strain has reduced levels of DHQ dehydratase, which if present would divert some of the metabolic flow into the biosynthesis of aromatic amino acids its blockage results in higher production of quinic acid. 

J. Frost and J. R. Knowles, 3-Deoxy-D-arabino-heptulosonic acid 7-phosphate Chemical synthesis and isolation from Escherichia coli auxotrophs, Biochemistry 23 4465 (1984). 

The product of the DAHP synthase, 3-deoxy-D-arabino-heptulosonate 7-phosphate, is shown in its cyclic hemiacetal form at the beginning of Eq. 25-2. Its conversion to 3-dehydroquinate is a multistep process that is catalyzed by a single enzyme, 14/15 which is the product of E. coli gene am B. The elimination of... 

The 3-deoxy D-arabino-heptulosonic acid 7-phosphate (DAHP, 34), intermediate of the shikimic acid pathway (cf. Sect. 2.2.4), has also been prepared... 

D. B. Sprinson, J. Rothschild, and M. Sprecher, The synthesis of 3-deoxy-D-arabino-heptulosonic acid 7-phosphate, J. Biol. Chem., 238 (1963) 3170-3175. 

Scheme 6.4.1. The shikimate biosynthetic pathway. The enzymes involved are (1) 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, (2) dehydroquinate synthase, (3) 5-...

Subsequently some doubt was cast on Mechanism D, because it has been shown1578 that the condensation occurs with partial retention of the geometric asymmetry of 0-phosphono-enolpyruvic-3(Z)-f and -3(E)-t acids (48a), so that, from the former, 3-deoxy-D-arabino-heptulosonate-3(S)-t 7-phosphate was the preponderant product. This... 

Phenolic compounds include a wide range of secondary metabolites that are biosynthesised from carbohydrates through the shikimate pathway [14]. This is the biosynthetic route to the aromatic amino acids, phenylalanine, tyrosine, and tryptophan, and only occurs in microorganisms and plants. In the first step, the glycolytic intermediate phosphoenol pyruvate and the pentose phosphate intermediate erythrose-4-phosphate are condensed to 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP), a step catalysed by DAHP synthase. Intermediates of the shikimate pathway are 3-dehydroquinate, shikimate, and chorismate (Fig. 1). Phenylalanine is biosynthesised from chorismate, and from phenylalanine all the phenylpropanoids. Quinate is produced from 3-dehydroquinate and incorporated into chlorogenic and isochlorogenic acids (caffeoyl quinic acids) by combination with caffeic acid. Gallic acid is produced from shikimate. 

Fig. (1). Phenolic metabolism. PEP (phospho enol pyruvate) E4P (erythrose 4-phosphate) DAHP (3-Deoxy-D-arabino-heptulosonate 7-phosphate) PAL (phenylalanine ammonia lyase). Stress transcriptionally activates the key enzymes of phenolic metabolism (PAL and DAHP synthase).

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