This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Pope, S. D.
Right arrow Articles by Stewart, V.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Pope, S. D.
Right arrow Articles by Stewart, V.

 Previous Article  |  Next Article 

Journal of Bacteriology, February 2009, p. 1006-1017, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01281-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Purine Utilization by Klebsiella oxytoca M5al: Genes for Ring-Oxidizing and -Opening Enzymes{triangledown}

Scott D. Pope,{dagger} Li-Ling Chen, and Valley Stewart*

Department of Microbiology, University of California, Davis, California 95616-8665

Received 11 September 2008/ Accepted 25 November 2008

The enterobacterium Klebsiella oxytoca uses a variety of inorganic and organic nitrogen sources, including purines, nitrogen-rich compounds that are widespread in the biosphere. We have identified a 23-gene cluster that encodes the enzymes for utilizing purines as the sole nitrogen source. Growth and complementation tests with insertion mutants, combined with sequence comparisons, reveal functions for the products of these genes. Here, we report our characterization of 12 genes, one encoding guanine deaminase and the others encoding enzymes for converting (hypo)xanthine to allantoate. Conventionally, xanthine dehydrogenase, a broadly distributed molybdoflavoenzyme, catalyzes sequential hydroxylation reactions to convert hypoxanthine via xanthine to urate. Our results show that these reactions in K. oxytoca are catalyzed by a two-component oxygenase (HpxE-HpxD enzyme) homologous to Rieske nonheme iron aromatic-ring-hydroxylating systems, such as phthalate dioxygenase. Our results also reveal previously undescribed enzymes involved in urate oxidation to allantoin, catalyzed by a flavoprotein monooxygenase (HpxO enzyme), and in allantoin conversion to allantoate, which involves allantoin racemase (HpxA enzyme). The pathway also includes the recently described PuuE allantoinase (HpxB enzyme). The HpxE-HpxD and HpxO enzymes were discovered independently by de la Riva et al. (L. de la Riva, J. Badia, J. Aguilar, R. A. Bender, and L. Baldoma, J. Bacteriol. 190:7892-7903, 2008). Thus, several enzymes in this K. oxytoca purine utilization pathway differ from those in other microorganisms. Isofunctional homologs of these enzymes apparently are encoded by other species, including Acinetobacter, Burkholderia, Pseudomonas, Saccharomyces, and Xanthomonas.

* Corresponding author. Mailing address: Department of Microbiology, University of California, One Shields Ave., Davis, CA 95616-8665. Phone: (530) 754-7994. Fax: (530) 752-9014. E-mail: vjstewart{at}ucdavis.edu

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

{dagger} Present address: Molecular Biology Interdepartmental Ph.D. Program and Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles, CA 90095-1489.

Journal of Bacteriology, February 2009, p. 1006-1017, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01281-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»