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Metabolism of 2-ketogluconate by Pseudomonas aeruginosa Kay, William Wayne

Abstract

The non-phosphorylated oxidative pathway of glucose dissimilation has been confirmed in Pseudomonas aeruginosa using whole cells and cell-free extracts. The oxidation of glucose to 2-ketogluconate was complete and stoichiometric in cell-free extracts and cell-free extracts of glucose grown cells were shown to be incapable of metabolizing 2-ketogluconate. It was shown that whole cells completely degraded 2-ketogluconate and quantitatively accumulated pyruvic acid in the presence of specific inhibitors. The initial step involved in 2-ketogluconate dissimilation was found to be exceptionally labile to the effects of a variety of metabolic inhibitors. The metabolism of 2-ketogluconate was demonstrated to involve the initial phosphorylation with adenosine triphosphate (ATP) as the phosphate donor. The resultant intermediate, 2-keto-6-phosphogluconate, was identified and was shown to undergo reduction by a nicotinamide adenine dinucleotide phosphate linked reductase to 6-phosphogluconate which, in turn, was metabolized to pyruvate by enzymes of the Entner-Doudoroff pathway. Radioactivity from 2-ketogluconate-C¹⁴ was rapidly incorporated into cellular constituents, primarily protein, by washed cell suspensions of P. aeruginosa, but oxidation of 2-ketogluconate did not involve the accumulation of keto-acid intermediates. The role of 2-ketogluconic acid as a key intermediate for the conservation of excess carbon under conditions where nitrogen is limiting was discussed.

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