Cloning and Characterization of Uronate Dehydrogenases from Two Pseudomonads and Agrobacterium tumefaciens Strain C58

Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, 02139, USA.
Journal of bacteriology (Impact Factor: 2.69). 03/2009; 191(5):1565-73. DOI: 10.1128/JB.00586-08
Source: PubMed

ABSTRACT 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 (k(cat)) with glucuronate as a substrate was higher than that with galacturonate; however, the Michaelis constant (K(m)) for galacturonate was lower than that for glucuronate. The A. tumefaciens enzyme was found to have the highest rate constant (k(cat) = 1.9 x 10(2) s(-1) on glucuronate), which was more than twofold higher than those of both of the pseudomonad enzymes.

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Available from: Tae Seok Moon, Jul 16, 2014
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    • "In bacteria the genes of a catabolic pathway are often organised in an operon. In the case of the udh gene however, it does not seem that the genes of the remaining pathway are in the same operon (Yoon et al. 2008). It might be that the genes necessary for growth on mucic acid are regulated in a different way than the udh and are consequently in a different operon. "
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