Phosphogluconate Dehydratase

6-Phosphogluconate dehydratase participates in the Entner-Doudoroff pathway, which plays a primary role in glucose metabolism in many microorganisms. The enzyme catalyzes the dehydration of 6-phosphogluconate to form 2-keto-3-deoxy-6-phosphpgluconate. 

The product, 2-keto-3-deoxy-6-phosphogluconate, was separated by chromatography at room temperature and a flow rate of 1 mL/min on a Dionex CarboPac PA-1 column (4 mm x 250 mm). The mobile phase was composed of 24 mM NaOH and 300 mM sodium acetate for 5 minutes, followed by a linear gradient to 700 mM sodium acetate in 10 minutes. A linear gradient back to the initial conditions was run in 5 minutes. Pulsed amperometric detection was used with a pulse train consisting of a 480 ms detection pulse at +80 mV, followed by pulses of 120 ms at +600 mV and 60 ms at -600 mV. 

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Gardner, P. R., and Fridovich, I. (1991). Superoxide sensitivity of the Escherichia coli 6-phosphogluconate dehydratase. J. Biol. Chem. 266, 1478-1483. 

Figure 9.80 Representative chromatographs of Entner-Doudoroff metabolites, (a) 6-Phosphogluconate dehydratase-catalyzed formation of 2-keto-3-deoxy-6-phosphogluconate (12.51 min). (b) Blank run for 6-phosphogluconate dehydratase-catalyzed formation of 2-keto-3-deoxy-6-phosphogluconate, (KDPG) 6-phosphogluconate omitted from assay. (From Taha and Deits, 1994.)...

Fe/S-containing dehydratases (aconitase, flimarase, 6-phosphogluconate dehydratase) are easily oxidized by superoxide, their Fe/S-cluster being unstable and loses ferrous ions. Simultaneously hydroxyl radical is formed, which is one of the most active oxidizer. It is able to attack nuclei acids, proteins and phospholipids. Contrary to hydroxyl radical, hydroperoxide. H 0 . forming after SAR reduction, is an inert hydrophobic molecule, which... 

Thus, phosphogluconate dehydratase yields 2-oxo-3-deoxyphosphogluconate as the product. When the reaction is carried out in 2HzO the 2H is incorporated with a random configuration at C-3, indicating that the enzyme catalyzes only the dehydration and that the tautomerization of the enol to the ketone is nonen-zymatic. 

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