Phosphoenolpyruvate synthetase specificity

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]. 

Studies on the regulation of the common pathway of aromatic biosynthesis in several micro-organisms have shown that control of the first reaction (Figure 1.2), the conversion of o-erythrose-4-phosphate (7) and phosphoenolpyruvate (8) to 3-deoxy-o-arabino-heptulosonic acid-7-phosphate (9, DAHP), catalysed by the enzyme DAHP synthetase (EC 4.1.2.15) is an important factor in the overall control of the pathway In a number of enteric bacteria this enzyme exists in multiple molecular forms each of which is under the feedback control of a specific end-product. Thus in Escherichia coli there are three DAHP synthetases (iso-enzymes), the activity and formation of which are controlled by the three aromatic amino acids The formation and activity of DAHP synthetase... 

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