Synthetases DAHP synthetase

Fig. 4.—The Condensation of Enolpyruvate Phosphate and n-Erythrose 4-Phosphate by 3-Deoxy-D-oro6mo-heptulosonic Acid 7-Phosphate Synthetase (DAHP synthetase).

Deoxy-D-araZu o-heptulosonate-7-phosphate synthetase (DAHPS) is the initial enzyme in the pathway responsible for the synthesis of aromatic compounds in microorganisms and plants. It catalyses the reaction shown in Equation (4) ... 

Enzymatic synthesis relying on the use of aldolases offers several advantages. As opposed to chemical aldolization, aldolases usually catalyze a stereoselective aldol reaction under mild conditions there is no need for protection of functional groups and no cofactors are required. Moreover, whereas high specificity is reported for the donor substrate, broad flexibility toward the acceptor is generally observed. Finally, aldolases herein discussed do not use phosphorylated substrates, contrary to phosphoenolpyruvate-dependent aldolases involved in vivo in the biosynthetic pathway, such as KDO synthetase or DAHP synthetase [18,19]. 

Other pyruvate- and phosphoenolpyruvate-dependent aldolases have been isolated and purified, but have not yet been extensively investigated for synthetic use. Those showing promise for future applications include, 3-deoxy-D-arabino-2-heptulosonic acid 7-phosphate (DAHP) synthetase (EC 4.1.2.15), 2-keto-4-hydroxyglutarate (KHG) aldolase (EC 4.1.2.31), and 2-keto-3-deoxy-D-gluconate (KDG) aldolase (EC 4.1.2.20). DAHP synthetase has been used... 

Scheme 5.40. Preparative scale production of DAHP by multi-enzyme synthesis. Ei = hexoki-nase, E2 = pyruvate kinase, E3 = transketolase + D-ribose 5-P, E4 = DHAP synthetase. P, = inorganic phosphate, P = PC>32. ...

DAHP synthetase, 251, 255 Dehydroquinase, 258 Dehydroshikimate riductase, 259 Dextrans, 341 acid hydrolysis of, 349 chain lengths of, 345, 346 cuprammonium complexes of, 355 electron microscope studies on, 349 enzymic synthesis of, 342, 345, 355 from sucrose, 342 flow birefringence studies on, 349 fructose-containing, 359 infrared absorption spectra of, 352 isolation of, 343... 

Deoxy-D-arabino-2-heptulosonic Acid 7-Phosphate (DAHP) Synthetase (E.C. 4.1.2.15)... 

In vivo, DAHP synthetase, also known as phospho-2-keto-3-deoxyheptanoate synthetase, catalyzes the synthesis of DAHP from PEP and D-erythrose 4-phosphate11591. DAHP is a key intermediate in the shikimate pathway for the biosynthesis of... 

Hexokinase, 2. Pyruvate kinase, 3. Transketolase + o-ribose 5-P, 4. DAHP synthetase Figure 14.1-25. Multi-enzyme synthesis of DAHP. 

Enzymes i, hexokinase ii, pyruvate iii, transketolase iv, DAHP synthetase... 

The 3-deoxy-D-ara6mo-2-heptulosonic acid 7-phosphate (DAHP) synthetase (EC 4.1.2.15) is an enzyme involved in the shikimic pathway of aromatic amino acids biosynthesis in bacteria and plants, where catalyzes the construction of 3-deoxy-D-ara6/ o-2-heptulosonic acid 7-phosphate from phosphoenolpyruvate and D-erythrose 4-phosphate [6]. Although 3-deoxy-D-ara6/H0-2-heptulosonic acid 7-phosphate (DAHP) synthetase has not been widely investigated it has been employed for the DAHP synthesis on preparative scale from D-fructose in multienzyme system [68], This one-pot synthesis was subsequently even more simplified by the results of further studies which indicated that it was more efficient and economical to use the whole cells containing a DAHP synthetase plasmid [69]. 

In Neurospora evidence has been presented that differential feedback inhibition of the three DAHP synthetase isozymes catalyzing the first reaction in the pathway plays a major role in the regulation of aromatic amino acid biosynthesis [43-45]. In addition to this type of conventional regulation, another type of regulation involving the channeling of later steps by means of a multienzyme complex has been proposed. 

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