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Journal of Bacteriology, July 2000, p. 3934-3941, Vol. 182, No. 14
Department of Microbiology and Immunology,
The Brody School of Medicine, East Carolina University, Greenville,
North Carolina 27858-4354
Received 23 February 2000/Accepted 25 April 2000
A cyclic version of the Entner-Doudoroff pathway is used by
Pseudomonas aeruginosa to metabolize carbohydrates. Genes
encoding the enzymes that catabolize intracellular glucose to pyruvate and glyceraldehyde 3-phosphate are coordinately regulated,
clustered at 39 min on the chromosome, and collectively form the
hex regulon. Within the hex cluster is an open
reading frame (ORF) with homology to the devB/SOL
family of unidentified proteins. This ORF encodes a
protein of either 243 or 238 amino acids; it overlaps the 5' end
of zwf (encodes glucose-6-phosphate
dehydrogenase) and is followed immediately by eda (encodes
the Entner-Doudoroff aldolase). The devB/SOL homolog was
inactivated in P. aeruginosa PAO1 by recombination with a
suicide plasmid containing an interrupted copy of the gene,
creating mutant strain PAO8029. PAO8029 grows at 9% of the wild-type
rate using mannitol as the carbon source and at 50% of the wild-type
rate using gluconate as the carbon source. Cell extracts
of PAO8029 were specifically deficient in 6-phosphogluconolactonase
(Pgl) activity. The cloned devB/SOL homolog complemented
PAO8029 to restore normal growth on mannitol and gluconate and restored
Pgl activity. Hence, we have identified this gene as pgl
and propose that the devB/SOL family members encode
6-phosphogluconolactonases. Interestingly, three eukaryotic glucose-6-phosphate dehydrogenase (G6PDH) isozymes, from human, rabbit, and Plasmodium falciparum, contain Pgl domains,
suggesting that the sequential reactions of G6PDH and Pgl
are incorporated in a single protein. 6-Phosphogluconolactonase
activity is induced in P. aeruginosa PAO1 by growth on
mannitol and repressed by growth on succinate, and it is expressed
constitutively in P. aeruginosa PAO8026 (hexR).
Taken together, these results establish that Pgl is an essential enzyme
of the cyclic Entner-Doudoroff pathway encoded by pgl, a
structural gene of the hex regulon.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
The Pseudomonas aeruginosa devB/SOL Homolog,
pgl, Is a Member of the hex Regulon and
Encodes 6-Phosphogluconolactonase
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, The Brody School of Medicine, East
Carolina University, Greenville, NC 27858-4354. Phone: (252) 816-2700. Fax: (252) 816-3104. E-mail: phibbspa{at}mail.ecu.edu.
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