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Journal of Bacteriology, March 2009, p. 1565-1573, Vol. 191, No. 5
0021-9193/09/$08.00+0     doi:10.1128/JB.00586-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Cloning and Characterization of Uronate Dehydrogenases from Two Pseudomonads and Agrobacterium tumefaciens Strain C58{triangledown} ,{ddagger}

Sang-Hwal Yoon, Tae Seok Moon, Pooya Iranpour,{dagger} Amanda M. Lanza, and Kristala Jones Prather*

Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139

Received 28 April 2008/ Accepted 30 November 2008

Uronate dehydrogenase has been cloned from Pseudomonas syringae pv. tomato strain DC3000, Pseudomonas putida KT2440, and Agrobacterium tumefaciens strain C58. The genes were identified by using a novel complementation assay employing an Escherichia coli mutant incapable of consuming glucuronate as the sole carbon source but capable of growth on glucarate. A shotgun library of P. syringae was screened in the mutant E. coli by growing transformed cells on minimal medium containing glucuronic acid. Colonies that survived were evaluated for uronate dehydrogenase, which is capable of converting glucuronic acid to glucaric acid. In this manner, a 0.8-kb open reading frame was identified and subsequently verified to be udh. Homologous enzymes in P. putida and A. tumefaciens were identified based on a similarity search of the sequenced genomes. Recombinant proteins from each of the three organisms expressed in E. coli were purified and characterized. For all three enzymes, the turnover number (kcat) with glucuronate as a substrate was higher than that with galacturonate; however, the Michaelis constant (Km) for galacturonate was lower than that for glucuronate. The A. tumefaciens enzyme was found to have the highest rate constant (kcat = 1.9 x 102 s–1 on glucuronate), which was more than twofold higher than those of both of the pseudomonad enzymes.

* Corresponding author. Mailing address: Department of Chemical Engineering, Room 66-458, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139. Phone: (617) 253-1950. Fax: (617) 258-5042. E-mail: kljp{at}mit.edu

{triangledown} Published ahead of print on 5 December 2008.

{ddagger} Supplemental material for this article may be found at http://jb.asm.org/.

{dagger} Present address: The University of Texas Health Science Center at San Antonio, San Antonio, TX.

Journal of Bacteriology, March 2009, p. 1565-1573, Vol. 191, No. 5
0021-9193/09/$08.00+0     doi:10.1128/JB.00586-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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