Shikimate kinase, aromatic amino acid

Schmidt, C.L. Daneel, H.-J. Schultz, G. Buchanan, B.B. Shikimate kinase from spinach chloroplasts. Purification, characterization and regulatory function in aromatic amino acid biosynthesis. Plant Physiol., 93, 758-766 (1990)... 

In B. subtilis the single DAHPS enzyme is repressed most strongly by tyrosine, but maximal repression required the presence of both tyrosine and phenylalanine [121]. Tryptophan appeared to play no role in repression eontrol of synthesis of the enzyme. Nester et al. [121] also reported that a mixture of the three aromatic amino acids repressed synthesis of DAHPS, dehydroquinate synthetase, and shikimate kinase noncoordinately, but had no effect on the level of dehydroquinase. 

Phosphorylation of 3-hydroxyl group of shikimate by shikimate kinase (EC 2.7.1.71) with ATP as a cosubstrate initiates the biosynthesis pathway of anthranilic acid [2], This step also presents the first step of the shikimate pathway, which is a metabolic route used by bacteria, fungi, and plants for the biosynthesis of many aromatic products such as lignins, alkaloids, flavonoids, benzoic acid, and plant hormones, in addition to the aromatic amino acids (phenylalaiune, tyrosine, and tryptophan). The sequential EPSP synthesis is catalyzed by EPSP synthase (EC 2.5.1.19) through the addition of phosphoenolpyruvate to 3-phospho-shikimate followed elimination of phosphate. EPSP synthase belongs to the family of transferases, specifically to those transferring aryl... 

Anthranilic acid (or o-amino-benzoic acid) is an aromatic acid with the formula C H NO, which consists of a substituted benzene ring with two adjacent, or "ortho- functional groups, a carboxylic acid, and an amine (Fig. 14.1). Anthranilic acid is biosynthesized from shikimic acid (for shikimic acid biosynthesis, see Chapter 10) following the chorismic acid-mediated pathway [1]. Based on its biosynthetic mechanism, shikimate is transformed to shikimate 3-phosphate with the consumption of one molecule of ATP, catalyzed by shikimate kinase. 5-Enolpyruvylshikimate-3-phosphate (EPSP) synthase is then catalyze the addition of phosphoenolpyruvate to 3-phospho-shikimate followed by the elimination of phosphate, which leads to EPSP. EPSP is further transformed into chorismate by chorismate synthase. Chorismate reacts with glutamine to afford the final product anthranilate and glutamate pyruvate catalyzed by anthranilate synthase (Fig. 14.1). 

---