Escherichia coli glutamate dehydrogenase

Lightfoot Metabolite fingerprinting in transgenic Nicotiana tabacum altered by the Escherichia coli glutamate dehydrogenase gene J. Biomed. Biotechnol. 2 2667g. 

Johnson, A.R., and Dekker, E.E. (1996) Woodward s reagent K inactivation of Escherichia coli L-threo-nine dehydrogenase Increased absorbance at 340-350 nm is due to modification of cysteine and histidine residues, not aspartate or glutamate carboxyl groups. Protein Sci. 5, 382-390. 

Prephenate (26) is converted to phenylpyruvate (28) in many bacterial systems. In some organisms, such as Escherichia coli, prephenic acid also is oxidatively aromatized to / -hydroxyphenylpyruvic acid (29) by a soluble, NAD+-de-pendent enzyme, prephenate dehydrogenase. p-Hydroxy-phenylpyruvic acid is then transaminated by the addition of L-glutamate and pyridoxal phosphate to yield L-tyrosine (30). 

In bacteria and other micro-organisms, unlike higher organisms, L-phenylalanine (1) is not normally a precursor of L-tyrosine (2). Davis postulate that in these organisms prephenic acid is the precursor of L-tyrosine (2) and subsequent work at the enzymic level by Schwink and Adams established this proposal. Thus in Escherichia coli prephenic acid (31) is oxidatively aromatised to p-hydroxyphenylpyruvic acid (33) by a soluble, NAD" dependent, enzyme—prephenate dehydrogenase. With appropriate fortification —addition of L-glutamate and pyridoxal phosphate as cofactors —extracts of Escherichia coli then convert p-hydroxyphenylpyruvic acid quantitatively to L-tyrosine by transamination. 

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