Quinic acid dehydrogenase

The bacterium Klebsiella pneumonia can use quinic acid as a carbon source for its growth the first step here is oxidation of quinic acid to 3-deoxyhydroquinate (DHQ), which is catalyzed by the enzyme quinic acid dehydrogenase. Actually, thermodynamics predicts that the reverse reaction is favored. So if a second bacterium, which made DHQ, had inserted into it the gene for the dehydrogenase, and if this second bacterim did not normally metabolize quinic acid, then this would result in the second organism synthesizing quinic acid from DHQ. 

Use of a cloned quinic acid dehydrogenase has led to the successful conversion of D-glucose into quinic acid which was further transformed into benzoquinone. ... 

Quercetin, biosynthesis of, 268 Quinic acid. See Cyclohexanecarboxylic acid, 1,3,4,5-tetrahydroxy-. dehydrogenase, 259... 

The linking molecules for both pathw s are 3-dehydroquinic acid and 3-dehydroshikimic acid. 3-dehydro-quinic acid can be formed in a one-step reaction catalysed by quinate-dehydrogenase from quinic acid, an abundant plant metabolite (Figure 2). 

Figure 2. The biosynthesis of 3-dehydroquinic acid and 3-dehydroshikimic acid from quinic acid (1... quinate-dehydrogenase 2... dehydrogenase).

During the elucidation of the aromatic biosynthetic pathway, compounds were found that appear to be made in side reactions. These include quinic acid, which is reversibly made from dehydroquinic acid through the action of a DPN-specific dehydrogenase. This enzyme is found in Aerobacter, but not in E. coli. 5-Phosphoshikimic acid is also accumulated by certain coli mutants, but has no known metabolic func-... 

Quinic acid is also found throughout the plant kingdom, usually with shikimic acid. It occurs as the free acid in many plants and its phenolic esters are also very common. The simplest assumption for the biosynthesis of quinic acid is through the reduction of 3-dehydroquinic acid, catalyzed by quinate dehydrogenase. However, because of the rare occurrence of this enzyme, the biosynthesis of quinic acid still remains to be explained. 

Mitsuhashi and Davis 213) also discovered a dehydrogenase that oxidizes quinic acid to dehydroquinic acid in certain mutants of Aerdbactor. In this instance DPN is the required pyridine nucleotide. The bacterial strains that contain this enzyme respond to quinate as a growth factor. This dehydrogenase was purified in the same manner and to about the same extent as dehydroshikimic reductase. The pH optimum of quinic dehydrogenase was found to be at 9.8 Km values obtained were 4.9 X 10" M for quinic acid and 1.4 X 10 M for DPN at pH 9.4. 

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